BUG-731: RoutedRegistration.close() should not throw

Routed RPC implementations should be allowed to unregister themselves
without incurring a checked exceptions. This allows downstream users to
elide having to deal with raw Exception.

Change-Id: Ia356c6272da3d22a375c954e192f79786ab42395
Signed-off-by: Robert Varga <rovarga@cisco.com>