When using mysql+pymysql in the connection uri, the server_version_info
tupple is (5, 5, 5, 10, 1, 18, u'MariaDB'), which makes the version check
incorrectly prevent using FULLTEXT index.
Using the last four elements from the tupple seems good enough to
mitigate this inconsistency.
Change-Id: I5db3b611535e197699ea5d331f7bd073a39a31c4