Fix checkstyle update for OpenDJ headers in unit and functional tests.

Checkstyle update for OpenDJ headers in unit and functional tests.

Enable the use of the caching mechanism used by CheckStyle to significantly reduce the time required for it to run during subsequent builds.

Update the build script to ensure that checkstyle is run on the unit tests and functional/integration tests. At the present time, this includes only ensuring that the CDDL header is included at the top of the file. It also updates three integration test source files to add a missing line break in the CDDL header.