Sync to deal with HandlerReject

[AgeManning]

Description

I've seen multiple instances when first booting and connecting to a single peer the peer immediately tries to disconnect, but not before sending a status to us. Sync then tries to download blocks from the single peer, but the RPC is in a shutdown state and returns an RPC Error of HandlerReject. As this is an internal tracking mechanism, we don't penalize the peer, but the sync algorithm continually retries to download blocks from the peer.

The algorithm should stop after 5 failed attempts, however there seems to be a loop going on that I didn't track. Alternatively, we should handle the HandleReject error in the sync algo's and remove the peer as a candidate from syncing blocks.

[AgeManning]

#2615 was the source of this error.