Add missing rwlock calls when access keynode.initial and keynode.managed

WARNING: ThreadSanitizer: data race Write of size 1 at 0x000000000001 by thread T1 (mutexes: write M1): #0 dns_keynode_trust lib/dns/keytable.c:836 #1 keyfetch_done lib/dns/zone.c:10187 #2 dispatch lib/isc/task.c:1152 #3 run lib/isc/task.c:1344 #4 (closed)

Previous read of size 1 at 0x000000000001 by thread T2 (mutexes: read M2):
#0 keynode_dslist_totext lib/dns/keytable.c:682
#1 dns_keytable_totext lib/dns/keytable.c:732
#2 named_server_dumpsecroots bin/named/server.c:11357
#3 named_control_docommand bin/named/control.c:264
#4 control_command bin/named/controlconf.c:390
#5 dispatch lib/isc/task.c:1152
#6 run lib/isc/task.c:1344
#7 <null> <null>

Location is heap block of size 241 at 0x000000000010 allocated by thread T3:
#0 malloc <null>
#1 default_memalloc lib/isc/mem.c:713
#2 mem_get lib/isc/mem.c:622
#3 mem_allocateunlocked lib/isc/mem.c:1268
#4 isc___mem_allocate lib/isc/mem.c:1288
#5 isc__mem_allocate lib/isc/mem.c:2453
#6 isc___mem_get lib/isc/mem.c:1037
#7 isc__mem_get lib/isc/mem.c:2432
#8 new_keynode lib/dns/keytable.c:346
#9 insert lib/dns/keytable.c:393
#10 dns_keytable_add lib/dns/keytable.c:421
#11 process_key bin/named/server.c:955
#12 load_view_keys bin/named/server.c:983
#13 configure_view_dnsseckeys bin/named/server.c:1140
#14 configure_view bin/named/server.c:5371
#15 load_configuration bin/named/server.c:9110
#16 loadconfig bin/named/server.c:10310
#17 named_server_reconfigcommand bin/named/server.c:10693
#18 named_control_docommand bin/named/control.c:250
#19 control_command bin/named/controlconf.c:390
#20 dispatch lib/isc/task.c:1152
#21 run lib/isc/task.c:1344
#22 <null> <null>

Mutex M1 is already destroyed.

Mutex M2 is already destroyed.

Thread T1 (running) created by main thread at:
#0 pthread_create <null>
#1 isc_thread_create pthreads/thread.c:73
#2 isc_taskmgr_create lib/isc/task.c:1434
#3 create_managers bin/named/main.c:915
#4 setup bin/named/main.c:1223
#5 main bin/named/main.c:1523

Thread T2 (running) created by main thread at:
#0 pthread_create <null>
#1 isc_thread_create pthreads/thread.c:73
#2 isc_taskmgr_create lib/isc/task.c:1434
#3 create_managers bin/named/main.c:915
#4 setup bin/named/main.c:1223
#5 main bin/named/main.c:1523

Thread T3 (running) created by main thread at:
#0 pthread_create <null>
#1 isc_thread_create pthreads/thread.c:73
#2 isc_taskmgr_create lib/isc/task.c:1434
#3 create_managers bin/named/main.c:915
#4 setup bin/named/main.c:1223
#5 main bin/named/main.c:1523

SUMMARY: ThreadSanitizer: data race lib/dns/keytable.c:836 in dns_keynode_trust

(cherry picked from commit 840cf7ad)

Closes #2191 (closed)