Update login histogram owners.

Remove people no longer working on the project and replace with self:
nkostylev@, antrim@, rsorkin@, ginkage@ -> achuith@

Also take ownership of a few metrics.

BUG=538294

Review URL: https://codereview.chromium.org/1437823006

Cr-Commit-Position: refs/heads/master@{#359192}
1 file changed