Quite an old comment but in case anybody else comes across this. This is covered in the comments in CrowdManager.h. But to repeat them here:
/*
* Actors that should be avoided, but are not being simulated by crowd (like players)
* should implement CrowdAgentInterface AND register/unregister themselves with crowd manager:
*
* UCrowdManager* CrowdManager = UCrowdManager::GetCurrent(this);
* if (CrowdManager)
* {
* CrowdManager->RegisterAgent(this);
* }
*/