greybus: move operation timeout teardown

Move the cancel_delayed_work() call so it's done separate from the
removing the operation from the pending list.

This should have been part of this commit:
    d3809f7 greybus: move timeout out of gb_operation_insert()

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>