Add test for customize container factory
Prevent failure of web app with parent context

ServerProperties formerly had an @OnMissingBeanCondition
that didn't restrict the hierarchy. It also asserts that
the current context (not including parents) contains such
a bean. This led to an inevitable failure when there was
an existing instance in the parent context.

Fixed by a) searching only the current context, b) not
adding a ServerProperties bean if the context is not a
web app.