Honour new test variable PIPVERSION
Honour new test variable PIPVERSION

This allows testing with unreleased pips, which is important to know
if something is going to cause us or our users trouble.

Change-Id: Icb3a9c1486c76b673d25a3d18792baad3d26c763

JioCloud/pbr,WiFast/pbr,varunarya10/pbr,openstack-dev/pbr,varunarya10/pbr,klmitch/pbr,openstack-dev/pbr,JioCloud/pbr,openstack-dev/pbr,WiFast/pbr,klmitch/pbr