tests: Work around race in check-iprop

We need to wait_for the changes to show up, not for log messages or log
entries.  The latter can come before the HDB writes are committed.

tests/kdc/check-iprop.in

@@ -197,10 +197,12 @@ check_pidfile_is_dead () {
 
 wait_for_slave () {
     wait_for "iprop versions to change and/or slave to catch up" get_iprop_ver "$@"
+    sleep 1
 }
 
 wait_for_slave2 () {
     wait_for "iprop versions to change and/or second slave to catch up" get_iprop_ver2 "$@"
+    sleep 1
 }
 
 wait_for_master_down () {