qemu-iotests/162: Fix leaked temporary files

qemu-iotests 162 left qemu-nbd.pid behind in the scratch directory, and
potentially a file called '42' in the current directory. Make sure to
clean it up after completing the tests.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

tests/qemu-iotests/162

@@ -28,6 +28,13 @@ echo "QA output created by $seq"
 here="$PWD"
 status=1	# failure is the default!
 
+_cleanup()
+{
+    rm -f "${TEST_DIR}/qemu-nbd.pid"
+    rm -f 42
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
 # get standard environment, filters and checks
 . ./common.rc
 . ./common.filter