Add option to use mysql_server as hive_metastore

Add option to use mysql_server as hive_metastore

### Changes

+ add roles/mysql_server/*
+ In group_vars/all
  + `metastore: postgresql/mysql`
+ In roles/cdh_hive_config/
  + modify hive configure template
  + add mysql java connector
+ move //Create hive database and user in postgresql// into //roles/postgresql_server//
+ In site.yml
  + choose metastore role by group var