[task scheduler] Fix CORS host for trigger endpoint
[task scheduler] Fix CORS host for trigger endpoint

BUG=skia:6412

Change-Id: I494d3260d9f54278f2efbe2947963e382f29eafa
Reviewed-on: https://skia-review.googlesource.com/10181
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

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