tests/int: log when teardown starts

This aids in failed test analysis by allowing to distinguish the output
of various commands being run as part of the test case from the output
of teardown command like runc delete.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

tests/integration/helpers.bash

@@ -727,6 +727,8 @@ function teardown_bundle() {
 	[ ! -v ROOT ] && return 0 # nothing to teardown
 
 	cd "$INTEGRATION_ROOT" || return
+	echo "--- teardown ---" >&2
+
 	teardown_recvtty
 	local ct
 	for ct in $(__runc list -q); do