ZOOKEEPER-2729: Cleanup findbug warnings in branch-3.4: Correctness Warnings

[afine]

No description provided.

[afine]

@rakeshadr @hanm

Both of the findbugs related issues here appear to be from from ZOOKEEPER-1045. There were checks for an array length of less than zero if (response != null && response.length < 0) {.

According to the java spec (http://docs.oracle.com/javase/specs/jls/se7/html/jls-10.html#jls-10.7) this is an impossible condition.

The public final field length, which contains the number of components of the array. length may be positive or zero.

So I just remove the clause from the if block, please let me know if I am missing something.

[afine]

The javadoc warning from jenkins appears to be unrelated to the patch:

[javadoc] /home/jenkins/jenkins-slave/workspace/PreCommit-ZOOKEEPER-github-pr-build/src/java/main/org/apache/zookeeper/server/PurgeTxnLog.java:207: warning - @return tag has no arguments.

The new findbugs appears to be incorrect as well.

[hanm]

lgtm.

[hanm]

merged, please close pr @afine.