recipe/pbs: drop ignore-known-hosts-file option

From now on, hosts keys will always be checked and there is no way
to disable the check

slapos/recipe/pbs.py

@@ -226,15 +226,9 @@ class Recipe(GenericSlapRecipe, Notify, Callback):
       (self.options['sshclient-binary'],
        parsed_url.username, parsed_url.hostname, parsed_url.port)))
 
-    # Create known_hosts file by default.
-    # In some case, we don't want to create it (case where we share IP mong partitions)
-    if not self.isTrueValue(self.options.get('ignore-known-hosts-file')):
-      # Migration code: if known_hosts file contains entry with just IP, then it
-      # is updated to use [IP]:port. It allows to share same IP among partitions
-      if parsed_url.hostname in known_hosts_file:
-        del known_hosts_file[parsed_url.hostname]
-      known_hostname = "[%s]:%s" % (parsed_url.hostname, parsed_url.port)
-      known_hosts_file[known_hostname] = entry['server-key'].strip()
+    # Create known_hosts file
+    known_hostname = "[%s]:%s" % (parsed_url.hostname, parsed_url.port)
+    known_hosts_file[known_hostname] = entry['server-key'].strip()
 
     notifier_wrapper_path = os.path.join(self.options['wrappers-directory'], slave_id)
     rdiff_wrapper_path = notifier_wrapper_path + '_raw'