Check for ubuntu16.04 where distribution is 'xenial'
Check for ubuntu16.04 where distribution is 'xenial'

Correcting the check introduced for ubuntu 16.04, where the distribution is 'xenial'

Change-Id: Ic828a602290217089909b236bee59d1965a6750f
Closes-Bug: #1643899

Juniper/contrail-fabric-utils,Juniper/contrail-fabric-utils