CLOUDSTACK-6531: stopping the router in case of command failures. Also added alerts for failures.

Signed-off-by: Jayapal <jayapal@apache.org>
(cherry picked from commit 59bf3559196a9452a1a048849f4f9971753d373b)
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

Conflicts:
	server/src/com/cloud/network/router/VirtualNetworkApplianceManagerImpl.java