Update min supported service version for Yoga
Update min supported service version for Yoga

Nova only supports compute services that are not older than version
N-1. So in Yoga the smallest supported nova compute version is Xena
and the smallest Xena service version is 57.

Change-Id: I709b3967c9e6e390016c003f9e5b33ae55708d28
Signed-off-by: Takashi Natsume <2c48eb5bf73c355a2d5583bc776dffa383cdf819@gmail.com>

mahak/nova,mahak/nova,mahak/nova,openstack/nova,openstack/nova,openstack/nova