tests: add test for pvscan --cache --background

regression test for a segfault in pvscan --cache --background
bug fixed by commit:
f8bf641095

test/shell/lvmetad-pvscan-nomda-bg.sh

@@ -0,0 +1,57 @@
+#!/bin/sh
+# Copyright (C) 2015 Red Hat, Inc. All rights reserved.
+#
+# This copyrighted material is made available to anyone wishing to use,
+# modify, copy, or redistribute it subject to the terms and conditions
+# of the GNU General Public License v.2.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+. lib/inittest
+
+test -e LOCAL_LVMETAD || skip
+test -e LOCAL_LVMPOLLD && skip
+
+kill $(< LOCAL_LVMETAD)
+rm LOCAL_LVMETAD
+
+aux prepare_devs 2
+
+pvcreate --metadatacopies 0 "$dev1"
+pvcreate --metadatacopies 1 "$dev2"
+vgcreate $vg1 "$dev1" "$dev2"
+lvcreate -n foo -l 1 -an --zero n $vg1
+
+# start lvmetad but make sure it doesn't know about $dev1 or $dev2
+aux disable_dev "$dev1" "$dev2"
+aux prepare_lvmetad
+lvs
+mv LOCAL_LVMETAD XXX
+aux enable_dev "$dev2" "$dev1"
+mv XXX LOCAL_LVMETAD
+
+aux lvmconf 'global/use_lvmetad = 0'
+check inactive $vg1 foo
+aux lvmconf 'global/use_lvmetad = 1'
+
+pvscan --cache --background "$dev2" -aay
+
+aux lvmconf 'global/use_lvmetad = 0'
+# FIXME: inconclusive. may be a timing issue
+check inactive $vg1 foo
+aux lvmconf 'global/use_lvmetad = 1'
+
+pvscan --cache --background "$dev1" -aay
+
+aux lvmconf 'global/use_lvmetad = 0'
+i=100
+while ! check active $vg1 foo; do
+	test $i -lt 0 && fail "Failed to autoactivate"
+	sleep .1
+	i=$((i-1))
+done
+aux lvmconf 'global/use_lvmetad = 1'
+
+vgremove -ff $vg1