Specify --host in 027_stream_regress.pl's pg_regress invocation.

Specify --host in 027_stream_regress.pl's pg_regress invocation.

The invocation of pg_regress in 027_stream_regress.pl didn't specify the
host. It ends up working on most systems because of connection
defaults. However, on windows it makes the test very slow unless
PG_TEST_USE_UNIX_SOCKETS is used.

The problem is that windows resolves "localhost" to ::0, 127.0.0.1, the server
started only listens on 127.0.0.1.  On windows refused TCP connections are
internally retried a few times, with back-off between tries, taking at least 2
seconds.

Noticed while investigating a complaint about the test's slow speed by Andrew
Dunstan.

Discussion: https://postgr.es/m/20220127220351.kyp3bdaukfytmoqx@alap3.anarazel.de