Add synchronization between IRadio callbacks and service creation.

Radio indications are sent by vendor ril on a separate thread and
can be received even before radio service is created and registered.
This is to avoid that race and make sure indication callbacks are
accessed only after service is created.

Test: Basic telephony sanity
Bug: 34363807
Merged-in: Iab11add5ca458476575c8b52d5e5878ff2b1d175
Change-Id: Iab11add5ca458476575c8b52d5e5878ff2b1d175
diff --git a/libril/ril_service.h b/libril/ril_service.h
index d5d4034..71b72bf 100644
--- a/libril/ril_service.h
+++ b/libril/ril_service.h
@@ -208,6 +208,8 @@
                   int indicationType, int token, RIL_Errno e, void *response,
                   size_t responselen);
 
+pthread_rwlock_t * getRadioServiceRwlock(int slotId);
+
 }   // namespace radio
 
 #endif  // RIL_SERVICE_H
\ No newline at end of file