Adapt wait_until_true

The code is copy&pasted from Neutron tree. This patch copies what
the Neutron patch [1] removing eventlet from wait_until_true does.

[1] https://review.opendev.org/c/openstack/neutron/+/937843

Change-Id: Ib8caf3140aed22da40bbe48518df5a1ca2ecf8d1
Signed-off-by: Jakub Libosvar <libosvar@redhat.com>

ovn_bgp_agent/tests/utils.py

@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import eventlet
+import time
 import uuid
 
 
@@ -52,12 +52,12 @@ def wait_until_true(predicate, timeout=60, sleep=1, exception=None):
     :param exception: Exception instance to raise on timeout. If None is passed
                       (default) then WaitTimeout exception is raised.
     """
-    try:
-        with eventlet.Timeout(timeout):
-            while not predicate():
-                eventlet.sleep(sleep)
-    except eventlet.Timeout:
-        if exception is not None:
-            # pylint: disable=raising-bad-type
-            raise exception
-        raise WaitTimeout('Timed out after %d seconds' % timeout)
+    start_time = time.time()
+
+    while not predicate():
+        elapsed_time = time.time() - start_time
+        if elapsed_time > timeout:
+            raise exception if exception else WaitTimeout(
+                _("Timed out after %d seconds") % timeout
+            )
+        time.sleep(sleep)