cros_workon: fix forall (broken by --host) :/
cros_workon: fix forall (broken by --host) :/

Review URL: http://codereview.chromium.org/2966016

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