DNS: Remove unnecessary DNS check from installer

Previously we were checking content of DNS before actually adding DNS
records for replicas. This is causing cycle in logic and adds weird
corner cases to the installer which can blow up on DNS timeout or so.

The check was completely unnecessary because the installer knows IP
addresses and name of the machine. Removal of the check makes
the installer more reliable.

https://fedorahosted.org/freeipa/ticket/5962

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

ipaserver/install/bindinstance.py

@@ -54,7 +54,7 @@ from ipalib.util import (validate_zonemgr_str, normalize_zonemgr,
                          normalize_zone, get_reverse_zone_default,
                          zone_is_reverse, validate_dnssec_global_forwarder,
                          DNSSECSignatureMissingError, EDNS0UnsupportedError,
-                         UnresolvableRecordError, verify_host_resolvable)
+                         UnresolvableRecordError)
 from ipalib.constants import CACERT
 
 if six.PY3:
@@ -837,14 +837,6 @@ class BindInstance(service.Service):
     def __add_master_records(self, fqdn, addrs):
         host, zone = fqdn.split(".", 1)
 
-        if not dns_zone_exists(zone, self.api):
-            # check if master hostname is resolvable
-            try:
-                verify_host_resolvable(fqdn)
-            except errors.DNSNotARecordError:
-                root_logger.warning("Master FQDN (%s) is not resolvable.",
-                                    fqdn)
-
         # Add forward and reverse records to self
         for addr in addrs:
             try: