Allow rebroadcasting(process) of existing block to start elections if pow is above active difficulty

Right now a node will only start elections/request votes of an existing unconfirmed block if pow is higher than existing pow for this block. This leads to an issue like now when you have problems confirming existing blocks, and have to keep upping the pow to get elections started. Or you could randomly have gotten an extremely high pow for the block to begin with.

Instead of requiring the pow to be higher, just requiring the the pow to be above active difficulty could make this easier for services and wallets to restart elections.

In addition it should not restart an election if it is in the active elections already, preventing a bad actor from rebroadcasting the same blocks multiple times.