Add Multiple Bot Setup to swarm_bot_setup
Add Multiple Bot Setup to swarm_bot_setup

Allow listing --bot multiple times or listing a file that lists all the slaves to setup.

BUG=


Review URL: https://chromiumcodereview.appspot.com/10854094

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@151097 0039d316-1c4b-4281-b951-d872f2087c98

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