rejigged mysql install procedure

Former-commit-id: e9af8074

roles/mysql/vars/Ubuntu_18.yml

 server_packages:
-  - python
-  - python-dev
-  - libmysqlclient-dev
-  - python-pip
-  - libapache2-mod-wsgi
-  - python-mysql.connector
-  - mysql-server
-  - python-mysqldb
+#  - python
+#  - python-dev
+#  - libmysqlclient-dev
+#  - python-pip
+#  - libapache2-mod-wsgi
+#  - python-mysql.connector
+#  - mysql-server
+#  - python-mysqldb
+ - mariadb-server
 
 client_packages:
   - python
   - mariadb-client
 
-sqlServiceName: "mysqld"
+sqlServiceName: "mariadb-server"