Don't execute queries for invalid parameters

https://forums.percona.com/t/multiple-errors-from-pmm-in-the-mariadb-sql-error-log-file/24323/4

The issue here is that PMM is repeatedly sending queries to the client database that will always result in error. PMM should be much smarter with regard to the client database flavor/version.

For example, "Unknown system variable ‘slow_query_log_always_write_time" in MariaDB 10.4. PMM should detect that the client is running MariaDB 10.4 and NOT execute that query in the first place. The forums post noted above has other examples of commands/variables that are not supported in MariaDB and thus they are logged as error SQL in MariaDB from PMM.