Pass simDevice to the shutdown method (MobileNativeFoundation#561)

Signed-off-by: Nan Wang <nanwang1101@yahoo.com>

Author: nanwng

bp/src/BPSimulator.m

@@ -127,7 +127,7 @@ - (NSString *)installApplicationWithHost:(NSString *)testHost withError:(NSError
         }];
         return nil;
     } else {
-        [self shutdownSimulatorWithError:errPtr];
+        [self shutdownSimulator:simDevice withError:errPtr];
         if(*errPtr) {
             [BPUtils printInfo:ERROR withString:@"Shutdown simulator failed with error: %@", [*errPtr localizedDescription]];
             [deviceSet deleteDeviceAsync:simDevice completionHandler:^(NSError *error) {
@@ -307,17 +307,20 @@ - (BOOL)useSimulatorWithDeviceUDID:(NSUUID *)deviceUDID {
     return YES;
 }
 
-- (BOOL)shutdownSimulatorWithError:(id *)error {
-    [BPUtils printInfo:INFO withString:@"Starting Safe Shutdown of %@", self.device.UDID.UUIDString];
+- (BOOL)shutdownSimulator:(SimDevice *)simDevice withError:(id *)error {
+    if (!simDevice) {
+        return NO;
+    }
+    [BPUtils printInfo:INFO withString:@"Starting Safe Shutdown of %@", simDevice.UDID.UUIDString];
 
     // Calling shutdown when already shutdown should be avoided (if detected).
-    if ([self.device.stateString isEqualToString:@"Shutdown"]) {
-        [BPUtils printInfo:INFO withString:@"Shutdown of %@ succeeded as it is already shutdown", self.device];
+    if ([simDevice.stateString isEqualToString:@"Shutdown"]) {
+        [BPUtils printInfo:INFO withString:@"Shutdown of %@ succeeded as it is already shutdown", simDevice];
         *error = nil;
         return YES;
     }
 
-    return [self.device shutdownWithError:error];
+    return [simDevice shutdownWithError:error];
 }
 
 - (void)bootWithCompletion:(void (^)(NSError *error))completion {
@@ -333,7 +336,7 @@ - (void)openSimulatorHeadlessWithCompletion:(void (^)(NSError *))completion {
     [self.device bootAsyncWithOptions:options completionHandler:^(NSError *bootError){
         NSError *error = [self waitForDeviceReady];
         if (error) {
-            [self shutdownSimulatorWithError:&error];
+            [self shutdownSimulator:self.device withError:&error];
             if (error) {
                 [BPUtils printInfo:ERROR withString:@"Shutting down Simulator failed: %@", [error localizedDescription]];
             }
@@ -584,7 +587,7 @@ - (void)deleteSimulatorWithCompletion:(void (^)(NSError *error, BOOL success))co
     }
     if (self.device) {
         [BPUtils printInfo:INFO withString:@"Shutting down Simulator"];
-        [self shutdownSimulatorWithError:&error];
+        [self shutdownSimulator:self.device withError:&error];
         if (error) {
             [BPUtils printInfo:ERROR withString:@"Shutting down Simulator failed: %@", [error localizedDescription]];
             completion(error, NO);