selftest: teardown the environments also on getting SIGPIPE

selftest: teardown the environments also on getting SIGPIPE

make test uses

selftest.pl | subuntu-filter.py ...

FAIL_IMMEDIATELY=1 lets subuntu-filter.py exit,
which generates SIGPIPE in selftest.pl.

We should handle this just like any other signal
and teardown all environments.

This should make the teardown process more reliable/verbose.

Pair-Programmed-With: Michael Adam <obnox@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Michael Adam <obnox@samba.org>
(cherry picked from commit b2803950fc439017680069813fc49255a3f0cbbf)

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10696
backport autobuild/selftest fixes from master

Autobuild-User(v4-0-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-0-test): Tue Jul 15 14:34:31 CEST 2014 on sn-devel-104