[rstp]fixes the linux hung when enable stp by command brctl

When user try to use linux command brctl stp br-lan on/off
to set up the stp, it will cause linux go hung.

This is because when rstp is not enabled, the commands brctl stp
br-lan on will avoke rstp, the rstp will call this command again,
and in this command, it use a lock, it cause deadlock, make the
kernel hung.

in this fixes, the command won't run the rstp again, so it won't
go into deadlock.

Change-Id: I4b7322f976ec00c8c65219a2be43a7173858b917
Signed-off-by: Zhu Ken <guigenz@codeaurora.org>

rstp/patches/90-fixes-linux-hang-using-brctl-enable-stp.patch

+diff -Nur a/bridge-stp rstp-2011-10-11/bridge-stp
+--- a/bridge-stp	2015-09-11 15:07:22.317566056 -0700
++++ rstp-2011-10-11/bridge-stp	2015-09-11 16:17:16.365671676 -0700
+@@ -50,12 +50,17 @@
+     daemon
+ }
+ 
++#when kernel start stp, we can't start the rstp again.
++#otherwise it will cause deadlock issue
++checkpid $pid_file || exit 1
++
+ case $2 in
+      start) 
+-	daemon
+-	exec /sbin/rstpctl rstp $bridge on ;;
++	exec /sbin/rstpctl rstp $bridge on
++	;;
+      stop)  
+-	exec /sbin/rstpctl rstp $bridge off ;;
++	exec /sbin/rstpctl rstp $bridge off
++	;;
+      *)
+      	echo "Unknown action:" $2
+ 	echo "Usage: bridge-stp <bridge> {start|stop}"