Increase the size of the (cinder) LVM loopback
Increase the size of the (cinder) LVM loopback

It has been a while since the last bump and it looks like if more
cinder tests are executed, 20GB is a better size, and it shouldn't
impact the controllers too much, even when they are virtual.

Change-Id: I8f29a2f54ae76425b93ba3e9011f7248130ef98a

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared