Add additional parsing to extract the "MariaDB" keyword from version string

Add additional parsing to extract the "MariaDB" keyword from version string

Enhanced MySQL/MariaDB version string parsing to accommodate for exotic
MariaDB version strings where the "MariaDB" word is embedded among other
alphanumeric characters such as "MariaDBV1".   This detection is critical in
order to correctly accomodate for API features that have split between MySQL
and MariaDB such as the "transaction_isolation" system variable.

Fixes: #4624
Change-Id: Iba4b56535855629a974b1e24e012b07383d24199