Remove support for opensuse

We haven't been testing the distro for a while in CI, e.g. in
Tempest, the jobs on opensuse15 haven't been executed for a year
now.
Therefore the patch removes opensuse support from devstack.

Closes-Bug: #2002900
Change-Id: I0f5e4c644e2d14d1b8bb5bc0096d1469febe5fcc
diff --git a/lib/rpc_backend b/lib/rpc_backend
index 743b4ae..bbb4149 100644
--- a/lib/rpc_backend
+++ b/lib/rpc_backend
@@ -52,20 +52,7 @@
     if is_service_enabled rabbit; then
         # Install rabbitmq-server
         install_package rabbitmq-server
-        if is_suse; then
-            install_package rabbitmq-server-plugins
-            # the default systemd socket activation only listens on the loopback interface
-            # which causes rabbitmq to try to start its own epmd
-            sudo mkdir -p /etc/systemd/system/epmd.socket.d
-            cat <<EOF | sudo tee /etc/systemd/system/epmd.socket.d/ports.conf >/dev/null
-[Socket]
-ListenStream=
-ListenStream=[::]:4369
-EOF
-            sudo systemctl daemon-reload
-            sudo systemctl restart epmd.socket epmd.service
-        fi
-        if is_fedora || is_suse; then
+        if is_fedora; then
             # NOTE(jangutter): If rabbitmq is not running (as in a fresh
             # install) then rabbit_setuser triggers epmd@0.0.0.0.socket with
             # socket activation. This fails the first time and does not get