Make sure unittest2 is installed before installing testtools
Make sure unittest2 is installed before installing testtools

As seen during sanity runs, On icehouse, testtools installation
fails if unittest2 is not already present
This change makes sure unitttest2 is always installed first

Change-Id: I2aa3f14bfb50a0d7c64b76acc1f53b0ee6cac80a

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