honor keyword silence in fifo MODAPP-118

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@9199 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_fifo/mod_fifo.c

@@ -454,6 +454,10 @@ SWITCH_STANDARD_APP(fifo_function)
 		}
 	}
 
+	if (moh && !strcasecmp(moh, "silence")) {
+		moh = NULL;
+	}
+
 	check_string(announce);
 	check_string(moh);
 	switch_assert(node);