Fixed engine tests

Some tests are periodically getting fail
and show AttributeError: _oslo_messaging_localcontext_

It's related with the fact that monkey patching
must be done before importing oslo.messaging.

Change-Id: I0c6d3ce60c046123f0fbf5ce43c7629ec525a39b

mistral/tests/unit/__init__.py

@@ -0,0 +1,25 @@
+# Copyright 2016 NEC Corporation.  All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import sys
+
+import eventlet
+
+eventlet.monkey_patch(
+    os=True,
+    select=True,
+    socket=True,
+    thread=False if '--use-debugger' in sys.argv else True,
+    time=True
+)