updating os plugin version

Author: earthmant

openstack.yaml

@@ -2,7 +2,7 @@ tosca_definitions_version: cloudify_dsl_1_3
 
 imports:
   - http://www.getcloudify.org/spec/cloudify/4.3.1/types.yaml
-  - http://www.getcloudify.org/spec/openstack-plugin/2.7.3/plugin.yaml
+  - http://www.getcloudify.org/spec/openstack-plugin/2.7.4/plugin.yaml
   - http://www.getcloudify.org/spec/utilities-plugin/1.5.2/plugin.yaml
   - http://www.getcloudify.org/spec/fabric-plugin/1.5.1/plugin.yaml
   - imports/manager-configuration.yaml