Add bpastene@ to //testing/buildbot/OWNERS.

Change-Id: Ife4a5f712ad0f054ffa7dbe3681142a6da94326e
Reviewed-on: https://chromium-review.googlesource.com/1042532Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557227}

testing/buildbot/OWNERS

 # This is reserved for people that are comfortably with buildbot recipes
 # and understand the implications of changing these files.
 
+bpastene@chromium.org
 dpranke@chromium.org
 jam@chromium.org
 jbudorick@chromium.org