ensure dig sets exitcode after local UDP connection failure
dig previously set an exit code of 9 when a TCP connection failed or when a UDP connection timed out, but when the server address is localhost it's possible for a UDP query to fail with ISC_R_CONNREFUSED. that code path didn't update the exit code, causing dig to exit with status 0. we now set the exit code to 9 in this failure case.
Closes #3235 (closed)