cros-workon: change forall into iterate
cros-workon: change forall into iterate

* Bend iterate to accept either list of packages or --all, following the new
semantics

Reintroduces commit dc3359ba7cd3d67886a958d580e83bdce9e14faf, with fixed list cmd

Review URL: http://codereview.chromium.org/3022003

sigma/coreos-scripts,gtank/scripts,endocode/scripts,BugRoger/scripts,zhang0137/scripts,vmware/coreos-scripts,mjg59/scripts,fivethreeo/scripts,trnubo/scripts,marineam/coreos-scripts,gtank/scripts,andrejro/coreos--scripts,smilart/scripts,marineam/coreos-scripts,mischief/scripts,coreos/scripts,BugRoger/scripts,coreos/scripts,vmware/coreos-scripts,fivethreeo/scripts,crawford/scripts,trnubo/scripts,sigma/coreos-scripts,gtank/scripts,zhang0137/scripts,nicescale/scripts,BugRoger/scripts,crawford/scripts,nicescale/scripts,crawford/scripts,mjg59/scripts,bcwaldon/coreos-scripts,smilart/scripts,glevand/coreos--scripts,vmware/coreos-scripts,zhang0137/scripts,mischief/scripts,mjg59/scripts,bcwaldon/coreos-scripts,bcwaldon/coreos-scripts,fivethreeo/scripts,trnubo/scripts,marineam/coreos-scripts,mischief/scripts,glevand/coreos--scripts,nicescale/scripts,endocode/scripts,sigma/coreos-scripts,andrejro/coreos--scripts,smilart/scripts,endocode/scripts,andrejro/coreos--scripts