Retry when getting RP zones in stress:rpz:* jobs

stress:rpz:fedora:40:amd64 jobs sometimes fail as they can't get RP zones from rpzserver.isc.org.

2024-06-28:01:10:02 INFO: acquiring list of names in response policy zones
2024-06-28:01:10:35 ERROR: Command 'dig +onesoa @rpzserver.isc.org adware.host.dtq. AXFR' failed:
;; Connection to 149.20.2.45#53(149.20.2.45) for adware.host.dtq. failed: timed out.
;; Connection to 149.20.2.45#53(149.20.2.45) for adware.host.dtq. failed: timed out.
; <<>> DiG 9.16.51-dev <<>> +onesoa @rpzserver.isc.org adware.host.dtq. AXFR
; (2 servers found)
;; global options: +cmd
;; connection timed out; no servers could be reached
;; Connection to 149.20.2.45#53(149.20.2.45) for adware.host.dtq. failed: timed out.
2024-06-28:01:10:35 ERROR: Make sure you can access rpzserver.isc.org RPZ relay system (VPN may be needed)
2024-06-28:01:10:35 ERROR: Getting RPZ names failed, file '/builds/isc-projects/bind9/output/rpz_names.sorted' is empty.

It might be just intermittent, and a retry after a short sleep might help.

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