The findbug version used by hadoop is pretty old (1.3.9). The old version of Findbugs itself have some bugs (like http://sourceforge.net/p/findbugs/bugs/918/, hit by HADOOP-10474).
Futhermore, Java 8 is only supported by findbugs 3.0.0 or newer.
It's a good time to bump the findbugs version to 3.0.0.
Bump the maven plugin versions too -moving the numbers into properties