Ask for CONFIG_NEUTRON_OVS_VXLAN_UDP_PORT with ML2

This patch is fixind the issue when ML2 is used with OVS and VXLAN tunneling

This patch is also fixing conflicts with OVS/LB plugin packages in case
of all-in-one installations.

Change-Id: Ie4f84ccc0636b72c5d25157fd25eadcf793472f0
Fixes: rhbz#1066519