[9.20] fix: usr: Fix a zone refresh bug

A secondary zone could fail to further refresh with new
versions of the zone from a primary server if named was
reconfigured during the SOA request step of an ongoing
zone transfer. This has been fixed.

Closes #5307

Backport of MR !10468

Merge branch 'backport-5307-zone-refresh-stuck-after-reconfiguration-fix-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!10495