ofagent: Fix VLAN usage for TYPE_FLAT and TYPE_VLAN

while ofagent uses OF1.3, the current coding incorrectly uses
OF1.0 terms in some places.  namely, _local_vlan_for_flat uses
0xffff to mean "no VLAN".  it should use OFPVID_NONE and
pop_vlan/push_vlan appropriately.  the same problem exists for
reclaim_local_vlan.

Closes-Bug: 1301144
Change-Id: I3df821fd72471f8bd84366e3b5a1cc7e3489156c
Merge "ofagent: Fix VLAN usage for TYPE_FLAT and TYPE_VLAN"