There were two TODO's from a prior CL where deprecated HostAuth methods
were removed.
1. Do not use a generated URI to determine if account settings have changed.
Instead, use the HostAuth structure for this purpose.
2. The account key in the HostAuth structure has been deprecated. Remove as
much of it as possible (until the schema of the host auth database changes,
we must still refer to it when adding rows).
In the process, HostAuth tests were broken out into a separate unit test
file.
Change-Id: I4075da09af168f734db7b20a9ef63d4178ac2064
fe68c0e7c2