tests/int/scheduler: require smp

This test case fails when there's a single CPU. Fix this by adding
"require smp".

While at it, document the test case and add a FIXME to maybe remove
this test later.

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

tests/integration/scheduler.bats

@@ -25,10 +25,21 @@ function teardown() {
 	[[ "${lines[2]}" == *"runtime/deadline/period parameters: 42000/1000000/1000000" ]]
 }
 
+# Checks that runc emits a specific error when scheduling policy is used
+# together with specific CPUs. As documented in sched_setattr(2):
+#
+#   ERRORS:
+#   ...
+#        EPERM  The CPU affinity mask of the thread specified by pid does not
+#        include all CPUs  in  the  system (see sched_setaffinity(2)).
+#
 @test "scheduler vs cpus" {
+	requires smp
+
 	update_config ' .linux.resources.cpu.cpus = "0"
 		| .process.scheduler = {"policy": "SCHED_DEADLINE", "nice": 19, "runtime": 42000, "deadline": 1000000, "period": 1000000, }'
 
 	runc run -d --console-socket "$CONSOLE_SOCKET" test_scheduler
 	[ "$status" -eq 1 ]
+	[[ "$output" == *"process scheduler can't be used together with AllowedCPUs"* ]]
 }