Fix integration test (shared context by accident)
Ensure the AuthenticationManager is created when needed

There was too much state really in the old implementation of
AuthenticationManagerConfiguration, and it was leading occasionally
to null pointers when method A assumed that method B had already
been called and it hadn't. This change manages to concentrate all the
references to an AuthenticationManagerBuilder into a single method
call, removoing the need for storing it at all.

Fixes gh-1556
Remove JDBC from secure-web sample

Fixes gh-1534