fix: dig - always set the default port when doing a UDP query

This commit ensures that the port is set before attempting a UDP
query. Before that a situation could appear when previous query have
completed over a different transport (that uses a dedicated port) and
then a UDP query will be attempted over the port of the previous
transport.

Closes: #4984.
Merge branch 'artem-debian-bug-1059582' into 'main'

See merge request isc-projects/bind9!9618