input/ipa_keepalive.c: make sure IPA keepalive FSM is registered

Change-Id: I36997b31f50fb1e051686a58dac09bc9ed391d17
Fixes: CID#206090
diff --git a/src/input/ipa_keepalive.c b/src/input/ipa_keepalive.c
index d8eec77..172a36f 100644
--- a/src/input/ipa_keepalive.c
+++ b/src/input/ipa_keepalive.c
@@ -213,7 +213,7 @@
 
 static __attribute__((constructor)) void on_dso_load(void)
 {
-	osmo_fsm_register(&ipa_keepalive_fsm);
+	OSMO_ASSERT(osmo_fsm_register(&ipa_keepalive_fsm) == 0);
 }