Updated openstack/openstack
Project: openstack/tempest  23738f52cf6aa040e9e95648fc7bd751e73c7e1c
null
Add some tests for os_update_readonly_flag

There is no test for os_update_readonly_flag api,
so add some for it.

Change-Id: Ice9a6ffea47dbaa492067f746edddcfbfc4eac4a