This patch introduces cinder_os_region_name parameters for cinder
backend, because global os_region_name parameter was replaced by this
cinder specific parameters[1].
[1] 410747822c9433c83fd4aec547d3e4c288502f90
Change-Id: I4a7c9ac97ff2f1c04b651ecbc89b3cb1c583f2f9