Use root_logger for verify_host_resolvable()

After discussion with Martin Basti we decided to standardize on root_logger
with hope that one day we will use root_logger.getLogger('module')
to make logging prettier and tunable per module.

https://fedorahosted.org/freeipa/ticket/5710

Reviewed-By: Martin Basti <mbasti@redhat.com>

install/tools/ipa-replica-manage

@@ -830,7 +830,7 @@ def enforce_host_existence(host, message=None):
         return
 
     try:
-        verify_host_resolvable(host, root_logger)
+        verify_host_resolvable(host)
     except errors.DNSNotARecordError as ex:
         if message is None:
             message = "Unknown host %s: %s" % (host, ex)