Fix launch_slaves.py
Fix launch_slaves.py

Instead of "svn cat", check out the file and keep updated locally.
(SkipBuildbotRuns)
Review URL: https://chromiumcodereview.appspot.com/13764004

git-svn-id: 32fc27f4dcfb6c0385cd9719852b95fe6680452d@8555 2bbb7eff-a529-9590-31e7-b0007b416f81

google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot