fsm: Make sure we call 'onenter' of new state, not old state

Change-Id: I1a0181c25d9debe935e86d97ddffc24675e56a5f
diff --git a/src/fsm.c b/src/fsm.c
index 67db182..31ed194 100644
--- a/src/fsm.c
+++ b/src/fsm.c
@@ -326,6 +326,7 @@
 
 	LOGPFSM(fi, "state_chg to %s\n", osmo_fsm_state_name(fsm, new_state));
 	fi->state = new_state;
+	st = &fsm->states[new_state];
 
 	if (timeout_secs) {
 		fi->T = T;