sql.pp: use $ha to allow installation on a single host
mysql.conf.erb: add statement to avoid wsrep on a single host
cloud_database_sql_spec.rb: add unit tests for a single host
sql.pp: set default value for ha
cloud_database_sql_spec.rb: move create monitoring db

* moved in openstack database sql with HA shared_examples
cloud_database_sql_spec.rb: remove unused data