This fixes a crash when we initialize nsNavBookmarks with a database that is out
of date (the schema version is less than the current one). Because the bookmark
service initializes the history service in its Init method, and the history
service tries to get the bookmark service if the database needs an upgrade, we
try to re-enter the bookmark service's constructor. Bad things happen.
Adds a test to ensure that we don't do this again.
r=dietrich
r=MaK77