Enable some serivce when on boot

Solve the devstack ./rejoin-stack.sh when is reboot-safe in RHEL 7.
Enable mysql, postgresql, rabbitmq-server, openvswitch service when on boot.

Change-Id: I3ce9fc58ccc76092ad08314de1c3c9339ebfb3b5
Related-Bug: #1486833
diff --git a/lib/databases/postgresql b/lib/databases/postgresql
index 78c7bed..261574f 100644
--- a/lib/databases/postgresql
+++ b/lib/databases/postgresql
@@ -101,6 +101,9 @@
         install_package postgresql
     elif is_fedora || is_suse; then
         install_package postgresql-server
+        if is_fedora; then
+            sudo systemctl enable postgresql-server
+        fi
     else
         exit_distro_not_supported "postgresql installation"
     fi