ZOOKEEPER-4792: Use jvm as the prefix for the memory env log.

Reviewers: maoling
Author: horizonzy
Closes #2112 from horizonzy/tune-the-jvm-env-log

zookeeper-server/src/main/java/org/apache/zookeeper/Environment.java

@@ -85,9 +85,9 @@ public class Environment {
         // Get memory information.
         Runtime runtime = Runtime.getRuntime();
         int mb = 1024 * 1024;
-        put(l, "os.memory.free", runtime.freeMemory() / mb + "MB");
-        put(l, "os.memory.max", runtime.maxMemory() / mb + "MB");
-        put(l, "os.memory.total", runtime.totalMemory() / mb + "MB");
+        put(l, "jvm.memory.free", runtime.freeMemory() / mb + "MB");
+        put(l, "jvm.memory.max", runtime.maxMemory() / mb + "MB");
+        put(l, "jvm.memory.total", runtime.totalMemory() / mb + "MB");
 
         return l;
     }

zookeeper-server/src/test/java/org/apache/zookeeper/server/admin/CommandsTest.java

@@ -155,7 +155,7 @@ public class CommandsTest extends ClientBase {
 
     @Test
     public void testEnvironment() throws IOException, InterruptedException {
-        testCommand("environment", new Field("zookeeper.version", String.class), new Field("host.name", String.class), new Field("java.version", String.class), new Field("java.vendor", String.class), new Field("java.home", String.class), new Field("java.class.path", String.class), new Field("java.library.path", String.class), new Field("java.io.tmpdir", String.class), new Field("java.compiler", String.class), new Field("os.name", String.class), new Field("os.arch", String.class), new Field("os.version", String.class), new Field("user.name", String.class), new Field("user.home", String.class), new Field("user.dir", String.class), new Field("os.memory.free", String.class), new Field("os.memory.max", String.class), new Field("os.memory.total", String.class));
+        testCommand("environment", new Field("zookeeper.version", String.class), new Field("host.name", String.class), new Field("java.version", String.class), new Field("java.vendor", String.class), new Field("java.home", String.class), new Field("java.class.path", String.class), new Field("java.library.path", String.class), new Field("java.io.tmpdir", String.class), new Field("java.compiler", String.class), new Field("os.name", String.class), new Field("os.arch", String.class), new Field("os.version", String.class), new Field("user.name", String.class), new Field("user.home", String.class), new Field("user.dir", String.class), new Field("jvm.memory.free", String.class), new Field("jvm.memory.max", String.class), new Field("jvm.memory.total", String.class));
     }
 
     @Test