Return the set of snapshot directories and non-snapshot directories
		under the given path.

def listSnapshotDir(kls, path):
		"""Return the set of snapshot directories and non-snapshot directories
		under the given path."""
		snapshotSet    = set()
		nonsnapshotSet = set()
		try:
			entryList = os.listdir(path)
			for e in entryList:
				if kls.isFilenameInteger(e): snapshotSet   .add(e)
				else:                        nonsnapshotSet.add(e)
		except FileNotFoundError: pass
		finally:
			return snapshotSet, nonsnapshotSet