Fix minor problem with autotest permissions
Fix minor problem with autotest permissions

When grabbing buildbot image and test artifacts, properly install the test artifacts as if they were built by the user (with the user as owner).

Review URL: http://codereview.chromium.org/703001

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