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

lib/databases/mysql

@@ -154,6 +154,7 @@ EOF
         fi
     elif is_fedora; then
         install_package mariadb-server
+        sudo systemctl enable mariadb
     elif is_ubuntu; then
         install_package mysql-server
     else

lib/databases/postgresql

@@ -101,6 +101,9 @@ EOF
         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