ovsdb-server: Announce bound listening ports as status:bound_port.

ovsdb-server: Announce bound listening ports as status:bound_port.

The administrator can request that OVSDB bind any available TCP port, but
in that case there is no easy way to find out what port it has bound.  This
commit adds that information as the "bound_port" key in the "status"
column.

Signed-off-by: Ben Pfaff <blp@nicira.com>