Fix bug where square bracket is not removed before appending new rule.
Fix bug where square bracket is not removed before appending new rule.

Change-Id: I5618b211abd69b4e3774fa6e4009183ef996a8d8

BUG=8815
TEST=run locally

Review URL: http://codereview.chromium.org/4498004

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