masternodesync: fix extra `RequestedMNAttempt` increment in the sporks flow.
masternodesync: fix extra `RequestedMNAttempt` increment in the sporks flow.

As we are increase the `RequestedMNAttempt` right after calling `SwitchToNextAsset()`, the mn list sync starts with an invalid extra sync attempt.

PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX