[ios-sdk] Fix issue where picker view contents would be cleared on to…

…ken refresh.

Summary:
Handlers that cleared picker view controller data when session was closed were also incorrectly
clearing it when tokens were refreshed, causing the control to briefly flash to a blank list.
Data should only be cleared if the session is actually closed.

Test Plan:
- Ran Scrumptious, BooleanOG, FriendPickerSample, PlacePickerSample with token refresh timeout artificially
set to 5 seconds -- consistently repro'd bug without this fix, no repro with this fix.

Revert Plan:

Reviewers: jacl, mmarucheck, gregschechte, ayden

Reviewed By: jacl

CC: msdkexp@

Differential Revision: https://phabricator.fb.com/D540547

Task ID: 1321635

src/FBFriendPickerViewController.m

@@ -291,7 +291,8 @@ - (void)observeValueForKeyPath:(NSString *)keyPath
                       ofObject:(id)object 
                         change:(NSDictionary *)change 
                        context:(void *)context {
-    if ([object isEqual:self.session]) {
+    if ([object isEqual:self.session] &&
+        self.session.isOpen == NO) {
         [self clearData];
     }
 }

src/FBPlacePickerViewController.m

@@ -404,7 +404,8 @@ - (void)observeValueForKeyPath:(NSString *)keyPath
                       ofObject:(id)object 
                         change:(NSDictionary *)change 
                        context:(void *)context {
-    if ([object isEqual:self.session]) {
+    if ([object isEqual:self.session] &&
+        self.session.isOpen == NO) {
         [self clearData];
     }
 }