ktls_tests: Ignore spurious errors from shutdown(2).

[jhb]

Summary

For some of the "bad size" tests, the remote end can notice the error
and drop the connection before the test program returns from write to
call shutdown. In that case, shutdown fails with ENOTCONN. Permit
these ENOTCONN errors without failing the test.

Sponsored by: Chelsio Communications

[olivier]

I'm testing the 3 reviews (D37691, D37692 and D37693) at the same time, at for the first build & test run, regression tests still failing:

• sys.kern.ktls_test.ktls_receive_aes128_cbc_1_1_sha1_bad_major
• sys.kern.ktls_test.ktls_receive_aes256_cbc_1_2_sha256_bad_minor
• sys.kern.ktls_test.ktls_receive_aes256_cbc_1_1_sha1_oversized_record
• sys.kern.ktls_test.ktls_receive_chacha20_poly1305_1_3_oversized_record

with same error : "tests/sys/kern/ktls_test.c:283: close(sv[1]) == 0 not met" for all