Improve MySQL unit test time by implementing a wipe-data only mechanism

MySQL and MariaDB variants can be extremely slow doing schema updates. The current mechanism creates and destroys the schema between each MySQL unit test. With dramatic increase in schema size and the number of unit tests, test execution has become untenable.

Rather than creating and destroying the schema each time, it should be sufficient for each test to determine if it has the correct schema version and then simply wipe the transient data from the database upon entry and exit.

If the schema version is incorrect (or non existent), the schema should be destroyed and recreated. In theory this should happen infrequently, once a environment's unit test schema is correct.