ktls_tests: Ignore errors from close for receive error tests.

For tests that send invalid data to a TLS socket to trigger read
errors the kernel may end up dropping the connection before close is
called at the conclusion of the test resulting in spurious ECONNRESET
errors from close. Ignore any errors from close for these tests.

PR: 268390
Reported by: olivier, Michal Gulbicki <michalx.gulbicki@intel.com>
Reviewed by: markj
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D37717