Deletion of SPLITTING node on split rollback should clear the region from RIT

If a failure happens in split before OFFLINING_PARENT, we tend to rollback the split including deleting the znodes created.
On deletion of the RS_ZK_SPLITTING node we are getting a callback but not remvoving from RIT. We need to remove it from RIT, anyway SSH logic is well guarded in case the delete event comes due to RS down scenario.