Fix upgrade when named.conf does not exist

Commit aee0d2180c adds an upgrade step
that adds system crypto policy include to named.conf.  This step
omitted the named.conf existence check; upgrade fails when it does
not exist.  Add the existence check.

Also update the test to add the IPA-related part of the named.conf
config, because the "existence check" actually does more than just
check that the file exists - it also check that it contains the IPA
bind-dyndb-ldap configuration section.

Part of: https://pagure.io/freeipa/issue/4853

Reviewed-By: Christian Heimes <cheimes@redhat.com>

ipaserver/install/bindinstance.py

@@ -93,6 +93,10 @@ def create_reverse():
 
 
 def named_conf_exists():
+    """
+    Checks that named.conf exists AND that it contains IPA-related config.
+
+    """
     try:
         with open(paths.NAMED_CONF, 'r') as named_fd:
             lines = named_fd.readlines()

ipaserver/install/server/upgrade.py

@@ -905,6 +905,10 @@ def named_add_server_id():
 def named_add_crypto_policy():
     """Add crypto policy include
     """
+    if not bindinstance.named_conf_exists():
+        logger.info('DNS is not configured')
+        return False
+
     if sysupgrade.get_upgrade_state('named.conf', 'add_crypto_policy'):
         # upgrade was done already
         return False