HADOOP-14380. Make the Guava version Hadoop which builds with configurable. Contributed by Steve Loughran

hadoop-project/pom.xml

@@ -90,6 +90,7 @@
     <findbugs.version>3.0.0</findbugs.version>
     <spotbugs.version>3.1.0-RC1</spotbugs.version>
 
+    <guava.version>21.0</guava.version>
     <guice.version>4.0</guice.version>
     <joda-time.version>2.9.4</joda-time.version>
 
@@ -519,7 +520,7 @@
       <dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
-        <version>21.0</version>
+        <version>${guava.version}</version>
       </dependency>
       <dependency>
         <groupId>com.google.code.gson</groupId>