[test][sockhash/map] Fix the test to work with kernels >= 5.15

Those tests have started to fail since kernel 5.15.
The restriction was lifted in https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=0c48eefae712c2fd91480346a07a1a9cd0f9470b

This diff makes the expected returned value to the call to `update_value` conditional
on the kernel version.

Tested on 5.15 (using a Ubuntu 22.04 host), which is representative of the kernel running in GH CI.
Also tested on Ubuntu 20.04 stock kernel:

```
$ docker run -ti \
                    --privileged \
                    --network=host \
                    --pid=host \
                    -v $(pwd):/bcc \
                    -v /sys/kernel/debug:/sys/kernel/debug:rw \
                    -v /lib/modules:/lib/modules:ro \
                    -v /usr/src:/usr/src:ro \
                    -e CTEST_OUTPUT_ON_FAILURE=1 \
                    bcc-docker-focal \
                    /bin/bash -c \
                    '/bcc/build/tests/wrapper.sh \
                        c_test_all sudo /bcc/build/tests/cc/test_libbcc "test sock*"'
===============================================================================
All tests passed (8 assertions in 2 test cases)

[22:40:55] chantra@focal:bcc git:(fix_sock_map_tests*) $ uname -a
Linux focal 5.4.0-122-generic iovisor#138-Ubuntu SMP Wed Jun 22 15:00:31 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
```

tests/cc/test_sock_table.cc

@@ -25,6 +25,14 @@
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
 
+// Prior to 5.15, the socket must be TCP established socket to be updatable.
+// https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=0c48eefae712c2fd91480346a07a1a9cd0f9470b
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 15, 0)
+ bool expected_update_result = false;
+#else
+ bool expected_update_result = true;
+#endif
+
 TEST_CASE("test sock map", "[sockmap]") {
  {
  const std::string BPF_PROGRAM = R"(
@@ -58,9 +66,8 @@ int test(struct bpf_sock_ops *skops)
  res = sk_map.remove_value(key);
  REQUIRE(!res.ok());
 
- // the socket must be TCP established socket.
  res = sk_map.update_value(key, val);
- REQUIRE(!res.ok());
+ REQUIRE(res.ok() == expected_update_result);
  }
 }
 
@@ -101,9 +108,8 @@ int test(struct bpf_sock_ops *skops)
  res = sk_hash.remove_value(key);
  REQUIRE(!res.ok());
 
- // the socket must be TCP established socket.
  res = sk_hash.update_value(key, val);
- REQUIRE(!res.ok());
+ REQUIRE(res.ok() == expected_update_result);
  }
 }