Added support for multiple vlans in ipv4 vdev mode

Added support for multiple vlans in ipv4 vdev mode

When the following conditions are met:
- ipv4
- vdev enabled
Then multiple vlans are supported.
Multiple vlans can be configured using the vlan_tag option within the port section of the config file.
Multiple (different) local_ipv4/prefix must then also be configured within the same section.

Note that for ipv6 multiple vlans are not supported (yet)
Also, when vdev is not enabled, multiple vlans are also not (yet) supported.

Change-Id: I38b6cd98ff2a0f484d1bf0910b15413ba21ae6d6
Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>