The image used for the tests is just treated as a blob, no guests
are booted using it so to speed up the tests when using slow
storage by switching to using cirros image. The cirros image is ~20
times smaller than the bionic one.
Increase wait attempts for availability of volume created from image
in CephRBDMirrorTest. This is taking longer as of Nautilus due to
switch to using juju storage backed by undercloud cinder taking
longer than prior method of directory-backed OSD devices.
Liam Young
Corey Bryant
Chris MacNaughton