Move `call_until_true` to tempest/lib

This `call_until_true()` is handy and could be used in Tempest plugins.
Let's move it to tempest/lib.

Also add some unit tests.

Change-Id: Ie379030baa336239e6027c8f3cdbeb74c561f66b
diff --git a/releasenotes/notes/move-call-until-true-to-tempest-lib-c9ea70dd6fe9bd15.yaml b/releasenotes/notes/move-call-until-true-to-tempest-lib-c9ea70dd6fe9bd15.yaml
new file mode 100644
index 0000000..543cf7b
--- /dev/null
+++ b/releasenotes/notes/move-call-until-true-to-tempest-lib-c9ea70dd6fe9bd15.yaml
@@ -0,0 +1,5 @@
+---
+deprecations:
+  - The ``call_until_true`` function is moved from the ``tempest.test`` module
+   to the ``tempest.lib.common.utils.test_utils`` module. Backward
+   compatibilty is preserved until Ocata.