core: Remove get image info call before images commands

BaseImageCommands calls for an image info updates its last modification
time on success and does nothing(!) on failure - the nothing is achieved
by updating the status in the DB and throwing an exception right
afterwards - which means a rollback to the update will be made.

also removed the unused VdcBllErrors.RESOURCE_MANAGER_VM_SNAPSHOT_MISSMATCH

Change-Id: I93e53f009030fe38d57274544146102010570814
Signed-off-by: Roy Golan <rgolan@redhat.com>