Test that blessed records can be transferred through a TupleQueue and
correctly decoded by another backend.  While touching the file, make
sure that force_parallel_mode settings only cover relevant tests.

Author: Thomas Munro, editorialized by Andres Freund
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/20170823054644.efuzftxjpfi6wwqs%40alap3.anarazel.de