[gold] Run metrics collection for ignores on a background process
[gold] Run metrics collection for ignores on a background process

Change-Id: Iad54231a70fecdae25b81994669da6373edca097
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/264642
Reviewed-by: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@google.com>
Commit-Queue: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@google.com>
Auto-Submit: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@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