[9.18] Honour the source-port when retrying in dns_dispatch
requested to merge 3986-handle-ISC_R_NOPERM-in-dns_dispatch-and-honour-the-source-port-9.18 into bind-9.18
When retrying in the DNS dispatch, the local port would be forgotten on ISC_R_ADDRINUSE, keep the configured source-port even when retrying.
Additionally, treat ISC_R_NOPERM same as ISC_R_ADDRINUSE.
Backport of !7806 (merged)
Closes #3986 (closed)