Drongo vs. 9.4 initdb TAP test

Buildfarm member drongo has been failing the initdb TAP test in the
9.4 branch for the last week or two:

# Running: rm -rf 'C:\prog\bf\root\REL9_4_STABLE\pgsql.build\src\bin\initdb\tmp_check\tmp_testAHN7'/*
'rm' is not recognized as an internal or external command,
operable program or batch file.
Bail out! system rm -rf 'C:\prog\bf\root\REL9_4_STABLE\pgsql.build\src\bin\initdb\tmp_check\tmp_testAHN7'/* failed: 256

The test has not changed; rather, it looks like drongo wasn't
trying to run it before.

This test is passing in the newer branches --- evidently due to
the 9.5-era commit 1a629c1b1, which removed this TAP script's
dependency on "rm -rf". So we should either back-patch that
commit into 9.4 or undo whatever configuration change caused
drongo to try to run more tests. I favor the former.

regards, tom lane