Replace the use of 'os_adm' with 'os_admin'

Property 'os_adm' has been moved to 'os_admin' in version Pike, and
it will be removed in version Queens. This patch is to replace the
usage of 'os_adm' with 'os_admin' in Tempest tests.

Change-Id: Ie4cf457d0a521910a82e41e7dad775df75d56587
3 files changed