Masternode: remove own mnb validation skip.
Masternode: remove own mnb validation skip.

The mnb can easily be invalid, it's arriving from the network.

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