GetServiceAsync is not thread safe

[cprice70]

GetServiceAsync crashes with the following exception, it appears that the collection is being modified at the same time that it is trying to enumerate the services. The exception happens when this line is called

var s = device.Services.First (x => x.ID == id);

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException (ExceptionResource resource) [0x0000b] in :0
at System.Collections.Generic.List1+Enumerator[Robotics.Mobile.Core.Bluetooth.LE.IService].MoveNextRare () [0x00016] in <filename unknown>:0 at System.Collections.Generic.List1+Enumerator[Robotics.Mobile.Core.Bluetooth.LE.IService].MoveNext () [0x00050] in :0
at System.Linq.Enumerable.First[IService](IEnumerable1 source, System.Func2 predicate, Fallback fallback) [0x00026] in :0
at System.Linq.Enumerable.First[IService](IEnumerable1 source, System.Func2 predicate) [0x00007] in :0
at Robotics.Mobile.Core.Bluetooth.LE.Extensions+c__AnonStorey1.<>m__1 (System.Object sender, System.EventArgs e) [0x0002a] in /Users/cprice1/Projects/Monkey.Robotics/Source/Platform Stacks/Robotics.Mobile.Core/Bluetooth/LE/Extensions.cs:78
at --- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000b] in :0
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in :0
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in :0
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in :0
at System.Runtime.CompilerServices.TaskAwaiter`1[Robotics.Mobile.Core.Bluetooth.LE.IService].GetResult () [0x00000] in :0
at IDS.BluetoothAdapter+c__async0.MoveNext () [0x000a4] in /Users/cprice1/Projects/Control/Control/IDS/IDS.BluetoothAdapter.cs:175
at --- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000b] in :0
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.m__1 (System.Object state) [0x00000] in :0