Fix default_track_gtids config value being ignored

[arthurschreiber]

When a new backend connection is opened, the session_track_gtids config variable would be set from the default specified in the proxysql configuration, but it was actually never sent to MySQL (via a SET SESSION command).

This changes the code to actually send the expected SET SESSION command.

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A reproducible test case can be found here: https://github.com/arthurschreiber/proxysql-issue/tree/default-session-track-gtid-issue

[pondix]

Automated message: PR pending admin approval for build testing

[renecannao]

ok to test

[renecannao]

@arthurschreiber :

A reproducible test case can be found here: https://github.com/github/proxysql-issues/tree/default-session-track-gtid-issue

The link doesn't work. Is it a private repo?

[arthurschreiber]

The link doesn't work. Is it a private repo?

Ah yes, I linked the wrong repo. I'll get that fixed asap.

[arthurschreiber]

Here's a working link: https://github.com/arthurschreiber/proxysql-issue/tree/default-session-track-gtid-issue

[renecannao]

Thank you @arthurschreiber !

[renecannao]

@arthurschreiber : can you please confirm the client are never using session_track_gtids=ALL_GTIDS ?

We need to make some change to the current implementation, because proxysql should track session_track_gtids with value OWN_GTID even if client sets it to OFF.
In other words, we need to decouple client setting from backend setting.