##### SUMMARY

`mysql_info` module doesn't show empty DBs. It uses following query in the code:

```
MariaDB [(none)]> SELECT table_schema AS 'name', SUM(data_length + index_length) AS "size" FROM information_schema.TABLES GROUP BY table_schema;
+--------------------+-----------+
| name               | size      |
+--------------------+-----------+
| d106953_tm         | 470728704 |
| information_schema |    212992 |
| mysql              |   6038300 |
| performance_schema |         0 |
+--------------------+-----------+
4 rows in set (0,005 sec)
```
But `show databases` show something else;
```
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| d106953_tm         |
| information_schema |
| innodb             |
| mysql              |
| performance_schema |
| testovic           |
| tm_web             |
| ttttt              |
+--------------------+
8 rows in set (0,001 sec)
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
`mysql_info` modules

##### ANSIBLE VERSION
```
ansible 2.9.1
  config file = /home/jiri/.ansible.cfg
  configured module search path = ['/home/jiri/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/jiri/stow/ansible/venv/lib/python3.6/site-packages/ansible
  executable location = /home/jiri/stow/ansible/venv/bin/ansible
  python version = 3.6.9 (default, Nov  7 2019, 10:44:02) [GCC 8.3.0]

```

##### OS / ENVIRONMENT
Amazon Linux 2
rh-mariadb103-3.3-5.el7.x86_64

##### STEPS TO REPRODUCE

* create empty via eg. via `mysql_db module`
* query via `mysql_info` what databases where found

##### EXPECTED RESULTS
should list even empty DBs

##### ACTUAL RESULTS

it seems only populated DBs are listed
"""Get user info."""
        res = self.__exec_sql('SELECT * FROM mysql.user')
        if res:
            for line in res:
                host = line['Host']
                if host not in self.info['users']:
                    self.info['users'][host] = {}
                user = line['User']
                self.info['users'][host][user] = {}
                for vname, val in iteritems(line):
                    if vname not in ('Host', 'User'):
                        self.info['users'][host][user][vname] = self.__convert(val)
    def __get_databases(self, exclude_fields):
        """Get info about databases."""
        if not exclude_fields:
            query = ('SELECT table_schema AS "name", '
                     'SUM(data_length + index_length) AS "size" '
                     'FROM information_schema.TABLES GROUP BY table_schema')
        else:
            if 'db_size' in exclude_fields:
                query = ('SELECT table_schema AS "name" '
                         'FROM information_schema.TABLES GROUP BY table_schema')
        res = self.__exec_sql(query)
        if res:
            for db in res:
                self.info['databases'][db['name']] = {}
                if not exclude_fields or 'db_size' not in exclude_fields:
                    self.info['databases'][db['name']]['size'] = int(db['size'])
    def __exec_sql(self, query, ddl=False):