pgsql: Move tablespace path re-creation from the makefiles to pg_regres

Move tablespace path re-creation from the makefiles to pg_regress

Moving this logic into pg_regress fixes a potential failure with
parallel tests when pg_upgrade and the main regression test suite both
trigger the makefile rule that cleaned up testtablespace/ under
src/test/regress. Even if pg_upgrade was triggering this rule, it has
no need to do so as it uses a different tablespace path. So if
pg_upgrade triggered the makefile rule for the tablespace setup while
the main regression test suite ran the tablespace cases, it would fail.

61be85a was a similar attempt at achieving that, but that broke cases
where the regression tests require to run under an Administrator
account, like with Appveyor.

Reported-by: Andres Freund, Kyotaro Horiguchi
Reviewed-by: Peter Eisentraut
Discussion: https://postgr.es/m/20201209012911.uk4d6nxcnkp7ehrx@alap3.anarazel.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/6c788d9f6aadb41d76a72d56149268371a7895ee

Modified Files
--------------
src/bin/pg_upgrade/test.sh | 1 -
src/test/regress/GNUmakefile | 21 +++++++--------------
src/test/regress/pg_regress.c | 14 ++++++--------
src/tools/msvc/vcregress.pl | 1 -
4 files changed, 13 insertions(+), 24 deletions(-)