Fix handling of array arguments in chromite cros_build_lib.
Fix handling of array arguments in chromite cros_build_lib.

Change-Id: Ibc8d603708bb239a125d0c642deecdc3a171ca63

BUG=chromium-os:9759
TEST=cros_build_lib.RunCommand(['ls', '-l'])

Review URL: http://codereview.chromium.org/5347008

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