GitLab

Fix number of buckets in AsyncDNS.ServerCount and SyncDNS.ServerFailureIndex UMA
histograms. Currently the value 9 falls in the bucket with value 8 which is
confusing. Results can be checked on uma.googleplex.com.

BUG=

Review URL: https://codereview.chromium.org/551873002

Cr-Commit-Position: refs/heads/master@{#296950}