Clean-up.

1. BasicOperationService::registerInvocation accepts BasicInvocation so deregisterInvocation() should accept the same.
2. BasicInvocationFuture explicitly declares its dependency on BasicOperationService rather than traversing fields Invocation -> NodeEngine -> OperationService and casting.
Merge pull request #3208 from jerrinot/cleanups/Operations-1

Minor clean-up in operations invocation