remove useless step in cleanup_rpc_backend

It shall not make dir of /var/run/openstack for the cleanup operation.

install_rpc_backend will make the directory, which is covered by another
take care of this.

Change-Id: I2bf1bfb4a6b409cc04f2d7b94dd58627e0134b71
diff --git a/lib/rpc_backend b/lib/rpc_backend
index ff87aae..c05bd8c 100644
--- a/lib/rpc_backend
+++ b/lib/rpc_backend
@@ -86,10 +86,6 @@
         else
             exit_distro_not_supported "zeromq installation"
         fi
-
-        # Necessary directory for socket location.
-        sudo mkdir -p /var/run/openstack
-        sudo chown $STACK_USER /var/run/openstack
     fi
 }