Shutdown polkitd properly on SIGTERM

While trying to break polkit using dfuzzer I couldn't make ASan/LSan
report _any_ memory leaks no matter how obvious they were. After a lot
of tinkering I managed to get the reports only when calling
__lsan_do_recoverable_leak_check() explicitly, which told me that the
shutdown __lsan_do_leak_check() is somehow getting skipped.

Turns out that polkitd does a "proper" shutdown on SIGINT (with which
ASan/LSan worked as expected), but not for SIGTERM. Fixing this, by
stopping the even loop even on SIGTERM, makes ASan/LSan happy (except
for the couple of memory leaks that were unfortunately hidden by this
behavior).

src/polkitbackend/polkitd.c

@@ -99,9 +99,9 @@ on_name_acquired (GDBusConnection *connection,
 }
 
 static gboolean
-on_sigint (gpointer user_data)
+on_sigint_sigterm (gpointer user_data)
 {
-  g_print ("Handling SIGINT\n");
+  g_print ("Handling %s\n", (const char *) user_data);
   g_main_loop_quit (loop);
   return TRUE;
 }
@@ -268,8 +268,12 @@ main (int    argc,
   loop = g_main_loop_new (NULL, FALSE);
 
   sigint_id = g_unix_signal_add (SIGINT,
-                                 on_sigint,
-                                 NULL);
+                                 on_sigint_sigterm,
+                                 "SIGINT");
+
+  sigint_id = g_unix_signal_add (SIGTERM,
+                                 on_sigint_sigterm,
+                                 "SIGTERM");
 
   sighup_id = g_unix_signal_add (SIGHUP,
                                  on_sighup,