connmgr: Reinitialise controllers if protocols changes

connmgr: Reinitialise controllers if protocols changes

This is allows protocol changes to take effect without needing
to restart ovs-vswitchd. However, connected controllers will
be disconnected regardless of if the OpenFlow protocol of the
session remains acceptable or not.

My feeling is that this is acceptable to avoid the complexity
of further modifications to ofconn and pvconn to allow live
updates of protocols.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>