[9.18] Allow some time to the root trust anchor to appear
requested to merge 3852-follow-up-from-9-18-merge-branch-3790-use-configured-udp-port-into-main-v9_18 into v9_18
Backport of MR !7493 (merged)
Following deleting the root trust anchor and reconfiguring the server it takes some time to for trust anchor to appear in 'rndc managed-keys status' output. Retry several times.
(cherry picked from commit 71dbd097)
Closes #3852 (closed)