Fix firmware packaging
Fix firmware packaging

BUG=none
TEST="run make_factory_package.sh --factory=X --release=X, doesn't crash"

Review URL: http://codereview.chromium.org/2858021

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