fix(database.py): change end_pattern for jmxserviceevent
fix(database.py): change end_pattern for jmxserviceevent

Change end_pattern to 'Stopped Scylla JMX.' in order to
show end_timestamp of JMXServiceEvent in raw_events.log properly.

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests