install the openstack-designate-api in the base stage

https://review.openstack.org/#/c/276676/ remove this line and break
the gate

TrivialFix

Change-Id: I0332caeffc6571801fba339108745f302487b33e

docker/designate/designate-base/Dockerfile.j2

@@ -9,6 +9,7 @@ MAINTAINER {{ maintainer }}
 # need the complete policy file because of some of the containers'
 # requiring it. Remove the package when the file is moved though.
 RUN yum install -y \
+        openstack-designate-api \
         openstack-designate-common \
         python-tooz \
     && yum clean all \