Hotfix a typo in master_mac_cfg.py
Hotfix a typo in master_mac_cfg.py

BUG=157151
TBR=nsylvain,pschmidt

Review URL: https://chromiumcodereview.appspot.com/11364126

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@166438 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build