[INTERNAL] cleaned up ConsistencyWatchdogHandler

Made fields and methods private and final. Removed dead variables,
renamed variables, and replaced SubMonitor class with IProgressMonitor
interface in method signatures.

Change-Id: Ib3f5f8a02abefaaa2915cf8a8d32e4c88c834816
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1880
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>