fix: test: Ignore ISC_R_CONNECTIONRESET in the TCP tests

On FreeBSD, the TCP connection callback could spuriously receive
ISC_R_CONNECTIONRESET even when connection to the loopback interface.
Skip the other checks in such case and graciously shutdown the TCP
connection.

Closes #4849

Merge branch '4849-dispatch_test-fails-in-connected_shutdown-on-freebsd' into 'main'

Closes #4849

See merge request isc-projects/bind9!9303