Equivalent transformation:
	* calls of pi_disconnect() in phase functions expanded.
	* since both do_pd_read_start() and do_pd_write_start()
	  are always called claimed (as the matter of fact,
	  all phase functions except do_pd_io() are), we can
	  replace call of pi_connect() with direct method call -
	  pi_claim() is no-op there.