change SERVER_HOST from 0.0.0.0 to localhost

web_config.yaml causes the app to spin up
at 0.0.0.0, which breaks OAuth. The OAuth
consumers are listening at localhost.
Therefore, changing SERVER_HOST to
localhost.

I've tested and this fixes the Google OAuth
functionality.

Bug: 59850
Change-Id: Idcb91b98c226d39636770cc5dea429200510d0dc
Merge "change SERVER_HOST from 0.0.0.0 to localhost"