This removes the DEFINED->FAILED transition and changes the
STARTED->FAILED transition to only occur if signalling didn't pass the
threshold. This ensures that it is always possible for activation to
occur, no matter what settings are chosen, or the speed at which blocks
are found.
Previously we used deployments that would timeout prior to Bitcoin's
invention, which allowed the deployment to still be activated in unit
tests. This switches those deployments to be truly never active.
