Fix server cleanup in test_multiple_create test

The above-mentioned test uses ServersClient.delete_server function to
delete servers. However, this function does not wait for the successful
deletion of the servers which sometimes leads to an error (see linked
bug).

This patch changes the test so that it uses
BaseV2ComputeTest.delete_server function which waits for the successful
deletion of the server.

Closes-Bug: #1954535
Closes-Issue: PRODX-35980
Change-Id: Ic1ed48fda03ce3c13198d2dd299b57d68b06e63d
diff --git a/tempest/api/compute/servers/test_multiple_create.py b/tempest/api/compute/servers/test_multiple_create.py
index 10c76bb..b464c45 100644
--- a/tempest/api/compute/servers/test_multiple_create.py
+++ b/tempest/api/compute/servers/test_multiple_create.py
@@ -15,6 +15,7 @@
 
 from tempest.api.compute import base
 from tempest.common import compute
+from tempest.common import waiters
 from tempest.lib import decorators
 
 
@@ -34,8 +35,15 @@
             wait_until='ACTIVE',
             min_count=2,
             tenant_network=tenant_network)
+
+        for server in servers:
+            self.addCleanup(waiters.wait_for_server_termination,
+                            self.servers_client,
+                            server['id'])
+
         for server in servers:
             self.addCleanup(self.servers_client.delete_server, server['id'])
+
         # NOTE(maurosr): do status response check and also make sure that
         # reservation_id is not in the response body when the request send
         # contains return_reservation_id=False