mgr/snap_schedule: catch all exceptions for cli

mgr/snap_schedule: catch all exceptions for cli

Any unknown exception causes the module to be unloaded and unresponsive.
So, it'll be ideal to catch all exceptions during command-line interaction
and report them instead of crashing with a traceback.

Fixes: https://tracker.ceph.com/issues/58195
Signed-off-by: Milind Changire <mchangir@redhat.com>
(cherry picked from commit 651fb2e3b515c80e9dc4a24638c9d1a0d487c729)

Conflicts:
	src/pybind/mgr/snap_schedule/module.py
	- minor conflicts due to changed variable names