Don't create replicas2 vm in zuul

Zuul is not capable of creating 3 VM due to the lack of memory.

Change-Id: I180e7f8e4ab07998b3c0fc66fe2e316dd8d42aba

trove_tempest_plugin/config.py

@@ -112,4 +112,12 @@ DatabaseGroup = [
         'rebuild_image_id',
         help="The new guest image ID used for rebuilding database instance."
     ),
+    cfg.BoolOpt(
+        "run_full_tests",
+        default=False,
+        help="Whether to run full tests for some tests. In the replication"
+             "test scenario, Trove will create 3 VMs for testing, In some"
+             "testing environment such as zuul, This will"
+             "cause the test to failed due to the lack of memory."
+    )
 ]

trove_tempest_plugin/tests/scenario/base_replication.py

@@ -99,6 +99,10 @@ class TestReplicationBase(trove_base.BaseTroveTest):
         new_db_names = [db['name'] for db in new_replica1_dbs]
         self.assertIn(db_name, new_db_names)
 
+        # In the zuul environment, the testing VM can not create the
+        # replica2 vm due to the lack of memory.
+        if not CONF.database.run_full_tests:
+            return
         # Create replica2
         LOG.info(f"Creating replica2 for instance {self.instance_id}")
         name = self.get_resource_name("replica-02")