ENG-5107: Java 1.6 -> 1.7 changes
ENG-5107: Remove concurrency classes backported from 1.7 to 1.6 and
just use the provided versions.
Merge remote-tracking branch 'origin/master' into eng5107-java17

Conflicts:
	src/frontend/org/voltcore/utils/CoreUtils.java
Merge pull request #854 from VoltDB/eng5107-java17

Eng5107 java17