test.call_until_true has been deprecated since Newton on Tempest side,
and now Tempest provides test_utils.call_until_true as the stable
library method. So this patch switches to use the stable method before
removing old test.call_until_true on Tempest side.
Change-Id: Iba2130aca93c8e6bccb4f8ed169424c791ebc127
Needed-by: Ide11a7434a4714e5d2211af1803333535f557370