Fix the way the SDK interprets UIWebViewDelegate errors
Fix the way the SDK interprets UIWebViewDelegate errors

Summary:
Currently if the facebook app encounters a UIWebViewDelegate error, it passes
it to the sdk in the error_code parameter. The SDK should know that if this
parameter is passed, an error occurred, which implies the user *didn't* cancel.
This fixes it.

Test Plan:
disconnected my laptop from the internet, went through the sso flow, verified
the sdk set userDidCancel to NO before calling [self
fbDialogNotLogin:userDidCancel].

DiffCamp Revision: 180310
Reviewed By: brent
CC: brent
Revert Plan:
OK

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