Fix buildslave offline alert text
Fix buildslave offline alert text

TBR=jcgregorio
BUG=skia:3961

Review URL: https://codereview.chromium.org/1669803002

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