Fix containment of `java::config`

[alexjfisher]

In 0dcd91b6e8d2b2519228c534fe4976e9d2a3a1d6 the anchor pattern was removed, but not replaced with anything and thus broke the containment of java::config. This restores the original behaviour by using contain.

As noted in the code comment, the declaration remains in the same place in the code as evaluation order is important. java::config is a private class and relies on variables from the base class's scope having been set before it is evaluated.

Also see https://github.com/puppetlabs/puppetlabs-java/pull/543#discussion_r1532211505