The gpstringsubs program replaces tokens in input .source test files
when creating output .sql/.out files for pg_regress. There were no
more callsites for the gp_glob_connect token however so remove that,
and also remove tests for gpwhich_<binary> tokens which aren't in
use in tests and thus might start failing randomly, which is exactly
what happened in another patch where Perl programs were no longer
incorrectly installed in PATH. Without this, removing the Perl test
apps from PATH results in errors like this:

	which: no get_ereport.pl in ( .. )
Reviewed-by: NHeikki Linnakangas <hlinnakangas@pivotal.io>