Removed redundant use of IDisposable and ManualResetEvent.

[Hellevar]

Fixed problem with usage of ManualResetEvent object.
original issue
As i can see there is no any reason to implement IDisposable and use ManualResetEvent inside Dispose method. With this fix everything works as expected.

[natemcmaster]

The purpose of implementing IDisposable and using a MRE is to ensure that services which might need to do some cleanup have a chance to gracefully exit before the process dies. While this might fix the ObjectDisposedException, it also removes one of the intentional features of this code.

Closing in favor of 38a5c76