Replace google-http-client imports with real guava imports.

Fixing up stray imports that probably exist as a result of IDE auto-completion.
That just came from running 'optimize imports' after changing the google import in this file (IndexerSQLMetadataStorageCoordinator was already there, a few lines up, but it was out of order). I'm in the habit of running that after making any changes to a file. Would it be better to not optimize imports unless more significant changes are being made to a file?