Small cleanup: remove unused local variable.
Small cleanup: remove unused local variable.

BUG=None
TEST=`./build_image --board=tegra2_kaen` still work
Change-Id: Ic3936cd2f300716ad48c04e504fbc0e1f36e0683
Reviewed-on: http://gerrit.chromium.org/gerrit/9928
Reviewed-by: Che-Liang Chiou <57969107b634cf11cb64e9d768fd46929066adab@chromium.org>
Tested-by: Hsinyu Chao <8b91762bdbe27d3121b311091d7ca5125e9a8df6@chromium.org>
Commit-Ready: Hsinyu Chao <8b91762bdbe27d3121b311091d7ca5125e9a8df6@chromium.org>

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