split up removal of obsolete jobs in _mergeGroups to keep _findErasures from having to handle jobs which we already know will not be applied
split up removal of obsolete jobs in _mergeGroups to keep _findErasures
from having to handle jobs which we already know will not be applied

fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary