Force mod_image_for_test to run inside chroot if outside
Force mod_image_for_test to run inside chroot if outside

Review URL: http://codereview.chromium.org/1818001

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