ZOOKEEPER-4331: add headers back in osgi artifact

Following up https://github.com/apache/zookeeper/pull/1722, I'm applying the change on master instead of 3.5.x as advised.

As an alternative to https://github.com/apache/zookeeper/pull/1726, this change employs bundle plugin to build another artifact of classifier "osgi".

The advantage would be bundle plugin remains employed to maintain the topology of versioned packages, and the original artifact without classifier is left untouched.

The disadvantage would be we've one more artifact delivered in this project.

```
$ ls zookeeper-server/target/ | grep jar$
zookeeper-3.5.9.jar
zookeeper-3.5.9-javadoc.jar
zookeeper-3.5.9-osgi.jar
zookeeper-3.5.9-sources.jar
zookeeper-3.5.9-tests.jar
```

Author: Wu, Xiaokai (Marvin) <marvinwu@ea.com>

Reviewers: Enrico Olivelli <eolivelli@apache.org>, Norbert Kalmar <nkalmar@apache.org>

Closes #1727 from bigmarvin/ZOOKEEPER-4331/add-new-osgi-artifact

pom.xml

@@ -820,6 +820,11 @@
             </execution>
           </executions>
         </plugin>
+        <plugin>
+          <groupId>org.apache.felix</groupId>
+          <artifactId>maven-bundle-plugin</artifactId>
+          <version>4.1.0</version>
+        </plugin>
       </plugins>
     </pluginManagement>
 

zookeeper-jute/pom.xml

@@ -150,6 +150,38 @@
             <skip>true</skip>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.apache.felix</groupId>
+        <artifactId>maven-bundle-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>build bundle</id>
+            <phase>package</phase>
+            <goals>
+              <goal>bundle</goal>
+            </goals>
+          </execution>
+        </executions>
+        <configuration>
+          <instructions>
+            <Import-Package>
+              *;resolution:=optional
+            </Import-Package>
+            <Export-Package>
+              org.apache.zookeeper.data,
+              org.apache.zookeeper.proto,
+              org.apache.zookeeper.txn,
+              !org.apache.zookeeper*,
+              org.apache.jute*
+            </Export-Package>
+            <Bundle-Name>ZooKeeper Jute Bundle</Bundle-Name>
+            <Bundle-DocURL>https://zookeeper.apache.org/doc/current/</Bundle-DocURL>
+            <Implementation-Build>${mvngit.commit.id}</Implementation-Build>
+            <Merge-Headers>!Implementation-Build,*</Merge-Headers>
+          </instructions>
+          <classifier>osgi</classifier>
+        </configuration>
+      </plugin>
     </plugins>
   </build>
 

zookeeper-server/pom.xml

@@ -277,7 +277,51 @@
           </systemPropertyVariables>
         </configuration>
       </plugin>
-	  
+
+      <plugin>
+        <groupId>org.apache.felix</groupId>
+        <artifactId>maven-bundle-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>build bundle</id>
+            <phase>package</phase>
+            <goals>
+              <goal>bundle</goal>
+            </goals>
+          </execution>
+        </executions>
+        <configuration>
+          <instructions>
+            <Import-Package>
+              io.netty.buffer;resolution:=optional,
+              io.netty.channel;resolution:=optional,
+              io.netty.channel.group;resolution:=optional,
+              io.netty.channel.socket.nio;resolution:=optional,
+              javax.management;resolution:=optional,
+              javax.security.auth.callback,
+              javax.security.auth.login,
+              javax.security.sasl,
+              org.ietf.jgss,
+              org.osgi.framework;resolution:=optional,
+              org.osgi.util.tracker;resolution:=optional,
+              org.slf4j,
+              *;resolution:=optional
+            </Import-Package>
+            <Export-Package>
+              !org.apache.zookeeper.data,
+              !org.apache.zookeeper.proto,
+              !org.apache.zookeeper.txn,
+              org.apache.zookeeper*
+            </Export-Package>
+            <Bundle-Name>ZooKeeper Bundle</Bundle-Name>
+            <Bundle-DocURL>https://zookeeper.apache.org/doc/current/</Bundle-DocURL>
+            <Implementation-Build>${mvngit.commit.id}</Implementation-Build>
+            <Merge-Headers>!Implementation-Build,*</Merge-Headers>
+          </instructions>
+          <classifier>osgi</classifier>
+        </configuration>
+      </plugin>
+
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-jar-plugin</artifactId>