rpc_backend: Conditionally enable rabbit on fedora

Change 4d8c03a added logic to enable rabbit on Fedora/CentOS systems
whether or not rabbit is enabled. This corrects that to only enable
rabbit when it is configured as such.

Change-Id: I270e79ff989176770d65df1ac0ac4e2c4382bb9a
Signed-off-by: Kyle Mestery <mestery@mestery.com>

Author: mestery

lib/rpc_backend

@@ -47,9 +47,9 @@ function install_rpc_backend {
     if is_service_enabled rabbit; then
         # Install rabbitmq-server
         install_package rabbitmq-server
-    fi
-    if is_fedora; then
-        sudo systemctl enable rabbitmq-server
+        if is_fedora; then
+            sudo systemctl enable rabbitmq-server
+        fi
     fi
 }