RequestProcessor plugins not executed on GroupRepository requests.

Request processor plugins are not executed on requests that originate from a group repository.

Setup:
Nexus is configured with a hosted M2Repository with RequestProcessor plugin which is a member of a MavenGroupRepository.

Steps:
1. Add the group repository to you maven project / settings and not the individual repository.
2. Build the maven project to execute a request on the group.

Expected:
1. The group repository will forward on the request to the maven repository
2. the maven repository will execute the request and execute the request processors associated to it.

Actual:
1. The group repository forwards the request but the request processor is never invoked. This is because the group repository calls org.sonatype.nexus.proxy.repository.AbstractRepository.retrieveItem(boolean, ResourceStoreRequest) which does not invoke AbstractRepository.checkConditions(ResourceStoreRequest, Action) and the RequestProcessors.