fastMode fails with MySQL and Hikari and AutoCommit=true

[rbygrave]

Refer to ebean-orm/ebean#3434

When MigrationRunner executes with:

• Hikari Connection Pool (it does not reproduce with ebean-datasource)
• AutoCommit = true
• MySQL (Due to Hikari treatment of the SQLException thrown with MySQL error codes)
• No actual migrations have run yet (this is expected)

... then we can reproduce this error.

The fastMode can fail (as expected) but the bug is that is performs connection.rollback() regardless of the AutoCommit mode [and it only should when autoCommit=false]. Hikari connection pool then reads the MySQL SQLException and infers that the connection is broken and should be evicted (imo this is a Hikari bug, using the ebean-datasource this issue doesn't reproduce).