unable to create mulitple snapshots from the same node

[naved001]

https://github.com/CCI-MOC/ims/blob/119e9ceaf62859b9c7e64f96fb33ab45b58af938/ims/einstein/operations.py#L325

this line always tries to create a snap, which prevents any subsequent calls to create snapshot. We should check if the snapshot exists, and create it only if it doesn't exist. We should always create a new rbd snapshot to get the latest changes.

[naved001]

All we have to do is delete the rbd snapshot when we are done creating the bmi snapshot. So just 2 more lines (rbd unprotect, rbd rm) at the end of this function should do the trick.