Bump OS_TEST_TIMEOUT for ironic-virtual d-s-g

The baremetal provisioning test is slow.  Bump the OS_TEST_TIMEOUT
used by Tempest from its default 500 sec.  We can tune this down once
we have a good average across both cloud providers.

Change-Id: I94ac8ec06fb602f44c4e4898527e0fc6535cde92
Merge "Bump OS_TEST_TIMEOUT for ironic-virtual d-s-g"