Remove 4 hour ban if initial headers not received
Remove 4 hour ban if initial headers not received

This ban is problematic when mining larger blocks and also
due to the single threaded message processing in the release
branch.  When very large blocks are being processed and a new
peer is trying to connect at the same time then a delay can
happen which exceeds the header download timeout. As a result
we can ban a node that is a good node.  By disconecting instead
the peer can try to re-connect again later.

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