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/tempest/scenario/test_minimum_basic.py b/tempest/scenario/test_minimum_basic.py
index f7c7434..dba1c92 100644
--- a/tempest/scenario/test_minimum_basic.py
+++ b/tempest/scenario/test_minimum_basic.py
@@ -17,6 +17,7 @@
 from tempest.common import waiters
 from tempest import config
 from tempest import exceptions
+from tempest.lib.common.utils import test_utils
 from tempest.scenario import manager
 from tempest import test
 
@@ -88,9 +89,9 @@
                     ['server'])
             return {'name': secgroup['name']} in body['security_groups']
 
-        if not test.call_until_true(wait_for_secgroup_add,
-                                    CONF.compute.build_timeout,
-                                    CONF.compute.build_interval):
+        if not test_utils.call_until_true(wait_for_secgroup_add,
+                                          CONF.compute.build_timeout,
+                                          CONF.compute.build_interval):
             msg = ('Timed out waiting for adding security group %s to server '
                    '%s' % (secgroup['id'], server['id']))
             raise exceptions.TimeoutException(msg)