mgr/smb: gracefully handle transient sqlitedb errors

Translate sqlite3.DatabaseError into a generic StoreUnavailable in
sqlite_store.py and handle it in cli.py and module.py instead of
letting it surface as an unhandled exception

Fixes: https://tracker.ceph.com/issues/78125
Signed-off-by: Avan Thakkar <athakkar@redhat.com>