MaxScale always advertises the SESSION_TRACK capability even with servers that don't support it (XPand)

If MaxScale is used with a XPand cluster, which doesn't support all the newer features that were introduced after MySQL 5.0, a client that expects the SESSION_TRACK functionality to work will not receive it. This also appears to be a problem with DBeaver which seems to query session_track_schema during its connection phase.

The solution is to check if any of the servers used by a service doesn't support the SESSION_TRACK capability and disable it if there is one.