Fixed PXB-2844 (Adjust logic to detect multi-threaded slave)

[altmannmarcelo]

Adjust logic to detect multi-threaded slave

Problem: MySQL 8.0.30 deprecated setting slave_parallel_workers or replica_parallel_workers to 0. Setting those variables to 1 has the same effect (replication is single threaded). PXB code to detect multithreaded was enabling MTS validation in case parallel workes was equal to 1.

Fix: Adjust the validation to only enable MTS if slave_parallel_workers or replica_parallel_workers are higher than 1.

[altmannmarcelo]

https://pxb.cd.percona.com/view/PXB%208.0/job/pxb80-single-platform-run/68/