Cleanup redundant isc_rwlock_init() result checks
requested to merge 1697-isc_rwlock_init-can-no-longer-fail-in-master-clean-up-calls-v9_16 into v9_16
(cherry picked from commit 3b11bacb)
Closes #1697 (closed), #2462 (closed)
(cherry picked from commit 3b11bacb)
Closes #1697 (closed), #2462 (closed)