server: remove peer from SyncManager on VerAckReceived
server: remove peer from SyncManager on VerAckReceived

Peers are now added to the SyncManager if we receive their verack, but
we'd still attempt to remove them from the SyncManager if we didn't
receive it.

tb00/btcd,btcsuite/btcd,dajohi/btcd,davecgh/btcd,tb00/btcd,dajohi/btcd,dajohi/btcd,davecgh/btcd,ltcsuite/ltcd,btcsuite/btcd,ltcsuite/ltcd