ovs-ofctl: Add --unixctl command line option.

This matches the option offered by some other Open vSwitch daemons.  I
intend to use it in tests in an upcoming commit.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>
connmgr: Demote service controllers too in ofconn_set_role().

Service controllers can set their roles, so it's necessary to demote them
to slaves if another controller becomes master.  Unfortunately the
'controllers' hmap only contains primary controllers, so this was omitted.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>
connmgr: Only send role status messages to OpenFlow 1.4+ controllers.

Only OpenFlow 1.4 and later support role status messages, but this code
tried to send them to all controllers, which caused an assertion failure.

Also, add tests to check that role status messages work, and that they
don't cause trouble with OF1.2.

Reported-by: Anup Khadka <khadka.py@gmail.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>