For Ubuntu, Install contrail-vrouter-generic package if one available for node's kernel version or install contrail-vrouter-dkms

Change-Id: I88bac092424ec8ad8a7b56567674a4e5019dd375
Partial-Bug: 1390796
Merge "For Ubuntu, Install contrail-vrouter-generic package if one available for node's kernel version or install contrail-vrouter-dkms"