Adding linux-image-extra as Recommended package for contrail-vrouter

In trusty, linux-image-generic package is split into linux-image and
linux-image-extra, ‘igb’ and display drivers are moved under extra package.

Change-Id: Ia41ec901c84df30e30771609a05eae2a86b1de6e
contrail-utils needs dependency on dpkg-dev
Added that dependency.

Change-Id: I9f6429e0defe67a9fab849c92adebd1d24b9995f
Closes-PR: 1390024
Allow other scripts on opencontrail-vrouter-netns

For example for script creating Docker service instance

Change-Id: If1ef83e7a4cd80c00732c012930d63f20547fe39