Properly handle attempting reorganization to an eligible block (#117)
Properly handle attempting reorganization to an eligible block (#117)

A continue statement was missing which could cause an issue when
attempting to iterate through different eligible blocks on the chain
tip to mine off of. The mining code was also amended to make it return
newly generated work later on in the code if for some reason not
enough voters were found, instead of just returning a nil template.
jcmincke/dcrd,jrick/btcd,jrick/btcd,jcmincke/dcrd,decred/dcrd,jcmincke/dcrd,jrick/btcd,jrick/dcrd,decred/dcrd,jrick/dcrd