ofproto: Support port mods in bundles.

ofproto: Support port mods in bundles.

Add support for port mods in an OpenFlow 1.4 bundle, as required for
the minimum support level by the OpenFlow 1.4 specification.  If the
bundle includes port mods, it may not specify the OFPBF_ATOMIC flag.
Port mods and flow mods in a bundle are always applied in order and
the consecutive flow mods between port mods are made available to
lookups atomically.

Note that ovs-ofctl does not support creating bundles with port mods.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>