selftest: Close STDIN_PIPE's write end for skipped daemons

selftest: Close STDIN_PIPE's write end for skipped daemons

Without this, any environment that skips any daemon will not shut down
properly. If a copy of a pipe's write end remains, closing one of them
won't cause the read end to be readable, i.e. the daemons waiting for
that won't exit properly.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>