##### 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 storage engines info."""
        res = self.__exec_sql('SHOW ENGINES')
        if res:
            for line in res:
                engine = line['Engine']
                self.info['engines'][engine] = {}
                for vname, val in iteritems(line):
                    if vname != 'Engine':
                        self.info['engines'][engine][vname] = val
    def __convert(self, val):
        """Convert unserializable data."""
        try:
            if isinstance(val, Decimal):
                val = float(val)
            else:
                val = int(val)
        except ValueError:
            pass
        except TypeError:
            pass
        return val
    def __get_global_variables(self):