cros_workon: refactor local manifest creation, kill duplicate entries (repo doesn't like them)
cros_workon: refactor local manifest creation, kill duplicate entries (repo doesn't like them)

	modified:   cros_workon

Review URL: http://codereview.chromium.org/3076046

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