Remove `MYSQL_OPT_RECONNECT` deprecation warning

[amatria]

Pull Request Prelude

• [x] I have followed [proper The Forgotten Server code styling][code].
• [x] I have read and understood the [contribution guidelines][cont] before making this PR.
• [x] I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

This PR removes the following deprecation warning: WARNING: MYSQL_OPT_RECONNECT is deprecated and will be removed in a future version. This PR fixes a race condition that may occur in Database::beginTransaction() too.

Issues addressed: #4624

[Zbizu]

thoughts on using goto statement in this code?