Support mariadb 10.2

Support mariadb 10.2

Fixed issue where CURRENT_TIMESTAMP would not reflect correctly
in the MariaDB 10.2 series due to a syntax change, where the function
is now represented as ``current_timestamp()``.

Fixes: #4096
MariaDB 10.2 now supports CHECK constraints (warning: use version 10.2.9
or greater due to upstream issues noted in :ticket:`4097`).  Reflection
now takes these CHECK constraints into account when they are present in
the ``SHOW CREATE TABLE`` output.

Fixes: #4098
Change-Id: I8666d61814e8145ca12cbecad94019b44af868e3