Recognize "!" flag in CTL_ON_{CREATE|START} to ignore failing commands

ecs/bin/ejabberdctl

@@ -278,14 +278,19 @@ post_waiter_loop()
     LIST=$@
     HEAD=${LIST%% ; *}
     TAIL=${LIST#* ; }
-    echo ":> ejabberdctl $HEAD"
+    HEAD2=${HEAD#\! *}
-    $0 $HEAD
+    echo ":> ejabberdctl $HEAD2"
+    $0 $HEAD2
     ctlstatus=$?
     if [ $ctlstatus -ne 0 ] ; then
+        if [ "$HEAD" != "$HEAD2" ] ; then
+            echo ":> FAILURE in command '$HEAD2' !!! Ignoring result"
+        else
             echo ":> FAILURE in command '$HEAD' !!! Stopping ejabberd..."
             $0 halt > /dev/null
             exit $ctlstatus
         fi
+    fi
     [ "$HEAD" = "$TAIL" ] || post_waiter_loop $TAIL
 }