Drop fast path use of keystoneauth1 sessions object.
There is no harm in passing all of the kwargs to both
glance and swift client objects and for swift, passing
just the session is not sufficient to correctly set
cacert and other security related settings.
The support for LXD KVM images uses the key 'combined_disk1-img_sha256'
and it creates this by looking for a file ending in '.img'.
On Xenial this file does not exist, instead we have '-disk1.img' and
'-uefi1.img' on Xenial with '-uefi1.img' being the same layout (gpt
partition with grub-efi) as the '.img' files that later releases have.
This patch adds a file extension match for '-uefi1.img', which will only
be found on Xenial, to create a 'combined_disk1-img_sha256' key for the
'lxd.tar.xz' item in streams to match LXD client expectations.