ios: fix deprecation warning

NSURLConnection sendSynchronousRequest is deprecated since iOS 9. Replace the
method by whjat's currently on RN master, which implements a modern alternative.

ios/sdk/src/RCTBridgeWrapper.m

 }
 
 - (BOOL)isPackagerRunning:(NSString *)host {
-    NSURL *url
-        = [serverRootWithHost(host) URLByAppendingPathComponent:@"status"];
-    NSURLRequest *request = [NSURLRequest requestWithURL:url];
-    NSURLResponse *response;
-    NSData *data = [NSURLConnection sendSynchronousRequest:request
-                                         returningResponse:&response
-                                                     error:NULL];
-    NSString *status = [[NSString alloc] initWithData:data
-                                             encoding:NSUTF8StringEncoding];
+    NSURL *url = [serverRootWithHost(host) URLByAppendingPathComponent:@"status"];
 
+    NSURLSession *session = [NSURLSession sharedSession];
+    NSURLRequest *request = [NSURLRequest requestWithURL:url];
+    __block NSURLResponse *response;
+    __block NSData *data;
+
+    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
+    [[session dataTaskWithRequest:request
+                completionHandler:^(NSData *d,
+                                    NSURLResponse *res,
+                                    __unused NSError *err) {
+                    data = d;
+                    response = res;
+                    dispatch_semaphore_signal(semaphore);
+                }] resume];
+    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
+
+    NSString *status = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
     return [status isEqualToString:@"packager-status:running"];
 }