tty.bats: add test cases when stdin is not a tty

Note that stdout/stderr are already redirected by bats'
`run` command, so the only way to get a controlling terminal
is to open /dev/tty (which fails if there isn't one).

Here's how I tested the failure to open /dev/tty:

> [root@kir-rhat ~]# ssh -T root@localhost cat ./runme
> cd /home/kir/go/src/github.com/opencontainers/runc
> ./runc run -b tst xxx-$$
> echo $?
>
> [root@kir-rhat ~]# ssh -T root@localhost ./runme
> time="2020-07-31T16:35:47-07:00" level=error msg="chdir tst: no such file or directory"
> 1

If anyone knows how to obtain an tty-less environment without using
ssh -T, please raise your hand.

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

tests/integration/tty.bats

@@ -11,6 +11,14 @@ function teardown() {
 	teardown_busybox
 }
 
+@test "runc run [stdin not a tty]" {
+	# stty size fails without a tty
+	update_config '(.. | select(.[]? == "sh")) += ["-c", "stty size"]'
+	# note that stdout/stderr are already redirected by bats' run
+	runc run test_busybox < /dev/null
+	[ "$status" -eq 0 ]
+}
+
 @test "runc run [tty ptsname]" {
 	# Replace sh script with readlink.
 	# shellcheck disable=SC2016
@@ -61,6 +69,18 @@ function teardown() {
 	[[ ${lines[1]} =~ 5 ]]
 }
 
+@test "runc exec [stdin not a tty]" {
+	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox
+	[ "$status" -eq 0 ]
+
+	# make sure we're running
+	testcontainer test_busybox running
+
+	# note that stdout/stderr are already redirected by bats' run
+	runc exec -t test_busybox sh -c "stty size" < /dev/null
+	[ "$status" -eq 0 ]
+}
+
 @test "runc exec [tty ptsname]" {
 	# run busybox detached
 	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox