Angelina Jolie wants someone (namely the UN) to end rape in war. It would be wonderful if that could happen, but in order for someone to do that they would need two things. The military might and the ability to project it, to force warring groups to exercise tighter discipline over their troops, and the political will to use it. Economic sanctions and stern admonitions will just go ignored - there must be a credible threat backing up the request to enforce anti-rape laws.
The UN doesn't have either of those. There isn't anyone out there who could do it without ending up in a thousand little and not so little wars with half of the world, so there probably isn't anyone capable of doing the job, and there definitely isn't anyone willing to do the job. All that has been accomplished by the actress is to bring up an issue that isn't getting solved short of someone conquering the world - and probably not even then.
If someone comes up with a workable plan for ending rape in warzones where the laws of war are usually ignored, I will happily eat my words.