On one system multiple volume and volume manger could be installed and
needs dedicated tgt config entries.
cinder-volumes, stack-volumes, nova-volumes are the default volume group
names.
/etc/tgt/conf.d/ files should be named based on the volume-group name.
The vg name is uniq on one system.
In devstack case the stack.conf is usable.
Changes:
* Rename conf.d/cinder.conf to conf.d/stack.conf
* Handle conf.d similary on all distribution
Change-Id: I856cdf4a21a414d2940d8f9d8b0b0368b1fad887