command line client does not warn about invalid --tls-version arguments

The mariadb / mysql command line client allows to request a specific TLS version to use via the --tls-version command line parameter, but when giving an unknown value as parameter it just ignores the option silently.

This is especially problematic as:

• version strings are case sensitive, TLSv1.1 works but tlsv1.1 doesn't
• MariaDB server/clients and Maxscale do not agree on syntax, MariaDB server and clients expect a dot between major and minor version part, Maxscale doesn't and has TLSv11 instead of TLSv1.1

Suggested fixes:

• make check case insensitive
• make the dot optional so that maxscale style version strings also work
• maybe also allow shorthands like v1.1 or just 1.1
• IMPORTANT: bail out with an error, or at least throw a warning, when getting an invalid/unknown version string