Hang around until killed by init at shutdown

init does two rounds of killing at shutdown:
a round of SIGTERMs and a round of SIGKILLs.

We want to stay alive until the SIGKILL round
so we ignore the SIGTERM signal.

src/main.c

@@ -1275,6 +1275,11 @@ main (int    argc,
   signal (SIGABRT, on_crash);
   signal (SIGSEGV, on_crash);
 
+  /* If we're shutting down we don't want to die until killed
+   */
+  if (state.mode == PLY_MODE_SHUTDOWN)
+    signal (SIGTERM, SIG_IGN);
+
   /* before do anything we need to make sure we have a working
    * environment.
    */