Update native/android/src/org/apache/cordova/facebook/ConnectPlugin.java

Cancel button on Feed Dialog does not trigger callback function.

When calling FB.ui for Dialog (method=feed):

iOS version returns upon:
send: response={"post_id":"???"}
cancel: response={}

BUT android differs and return upon:
send: response={"post_id":"???"}
cancel: callback function NOT called at all

Thus my proposed changes.