Chore: Fix image volume sizes and image flavors

In nearlly all cases, the v3 flavors provide larger disks by default
than were being defined. Using the pre-defined disk sizes will
significantly speed up the instance creation as well as improve the disk
i/o

* Remove nearly all volume size declarations so we pick up faster disks
* Update the outstanding flavors that were on non-v3 to a v3 variant

Issue-ID: CIMAN-33
Change-Id: I91be4239af2ac2bd503c4738dbe94ac03ff6718b
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>