Skip redundant sync messages.

SignalServiceKit/src/Devices/OWSDevice.m

@@ -46,13 +46,10 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
 {
     OWSAssert(dbConnection);
 
-    @synchronized(self)
-    {
     return [dbConnection boolForKey:kTSStorageManager_MayHaveLinkedDevices
                        inCollection:kTSStorageManager_OWSDeviceCollection
                        defaultValue:NO];
 }
-}
 
 - (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection
 {
@@ -67,13 +64,10 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
 {
     OWSAssert(transaction);
 
-    @synchronized(self)
-    {
     [transaction setObject:@(value)
                     forKey:kTSStorageManager_MayHaveLinkedDevices
               inCollection:kTSStorageManager_OWSDeviceCollection];
 }
-}
 
 - (BOOL)hasReceivedSyncMessageInLastSeconds:(NSTimeInterval)intervalSeconds
 {