Prevent dismissWithSuccess:animated from being called twice
Prevent dismissWithSuccess:animated from being called twice

Summary:
see https://github.com/facebook/facebook-ios-sdk/issues#issue/161

Test Plan:
verified it was called only once

DiffCamp Revision: 186903
Reviewed By: brent
CC: brent
Revert Plan:
OK

1234-/facebook-ios-sdk,hibu/facebook-ios-sdk,TimeIncOSS/facebook-ios-sdk,tipbit/facebook-ios-sdk,tipbit/facebook-ios-sdk,Subsplash/facebook-ios-sdk,TimeIncOSS/facebook-ios-sdk,ArtLapitski/facebook-ios-sdk,Citrrus/facebook-ios-sdk,wooga/facebook-ios-sdk,hibu/facebook-ios-sdk,TimeIncOSS/facebook-ios-sdk,hibu/facebook-ios-sdk,ArtLapitski/facebook-ios-sdk,Amnysia/facebook-ios-sdk,flovilmart/facebook-ios-sdk,flovilmart/facebook-ios-sdk,flovilmart/facebook-ios-sdk,taptaptap/facebook-ios-sdk,anthonylai/facebook-ios-sdk,ArtLapitski/facebook-ios-sdk,taptaptap/facebook-ios-sdk,ShareKit/facebook-ios-sdk,wooga/facebook-ios-sdk,FiftyThree/facebook-ios-sdk,Amnysia/facebook-ios-sdk,FiftyThree/facebook-ios-sdk,Subsplash/facebook-ios-sdk,tipbit/facebook-ios-sdk,beamly/facebook-ios-sdk,1234-/facebook-ios-sdk,anthonylai/facebook-ios-sdk,hibu/facebook-ios-sdk,shepting/facebook-ios-sdk,FiftyThree/facebook-ios-sdk,ShareKit/facebook-ios-sdk,1234-/facebook-ios-sdk,Subsplash/facebook-ios-sdk,beamly/facebook-ios-sdk,1234-/facebook-ios-sdk,shepting/facebook-ios-sdk,wooga/facebook-ios-sdk,flovilmart/facebook-ios-sdk,Citrrus/facebook-ios-sdk,ShareKit/facebook-ios-sdk,hibu/facebook-ios-sdk,Citrrus/facebook-ios-sdk,shepting/facebook-ios-sdk,anthonylai/facebook-ios-sdk,Amnysia/facebook-ios-sdk,flovilmart/facebook-ios-sdk,ArtLapitski/facebook-ios-sdk,shepting/facebook-ios-sdk,1234-/facebook-ios-sdk,shepting/facebook-ios-sdk,taptaptap/facebook-ios-sdk,beamly/facebook-ios-sdk