migration: Trace event and migration event are different things

We can want the trace event even without migration events enabled.

Reported-by:  Wen Congyang <ghostwcy@gmail.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/migration.c

@@ -216,7 +216,6 @@ static void migrate_generate_event(int new_state)
 {
     if (migrate_use_events()) {
         qapi_event_send_migration(new_state, &error_abort);
-        trace_migrate_set_state(new_state);
     }
 }
 
@@ -528,6 +527,7 @@ void qmp_migrate_set_parameters(bool has_compress_level,
 static void migrate_set_state(MigrationState *s, int old_state, int new_state)
 {
     if (atomic_cmpxchg(&s->state, old_state, new_state) == old_state) {
+        trace_migrate_set_state(new_state);
         migrate_generate_event(new_state);
     }
 }