[Bugfix beta] container.has should not cause injections to be run.

This fixes an issue, were merely checking the existence of a potential
container managed object could cause thrashing cycles. Only if
injection rules already contained a cycle.
[DOC] Adds needs docs for nested controller
Merge pull request #3841 from twokul/nested-controller-docs

[DOC] Adds needs docs for nested controller
Merge pull request #3840 from stefanpenner/container-has-should-be-idempotent

[Bugfix beta] container.has should not cause injections to be run.