core: Fixed modifiers of SlaValidator.log

Made the log private static final, as it ought to be by Java's
conventions.

Note that this patch fixes the MS_SHOULD_BE_FINAL FindBugs warning on
this class.

Change-Id: I131597533b09a395b1a1bc0891e4338a1a47e73a
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: EvenDistributionBalancePolicyUnit's comparators

Fixed modifiers in these comparators to increase performance and fix the
MS_SHOULD_BE_FINAL FindBugs warnings on these classes.

Change-Id: Ice42566f82dccfb66624d7054b52948220ced3ea
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Remove VdcException

This exception is not used anywhere in the codebase, and can safely be
removed.

Change-Id: I376f853585c18e36f6e2ee6d57c617851b329480
Signed-off-by: Allon Mureinik <amureini@redhat.com>