fix for ganeti xen instance migration

hv_xen.py

--- hv_xen.py   2021-02-01 18:04:47.850790870 +0100
+++ hv_xen.py   2021-02-01 18:07:58.119056797 +0100
@@ -799,7 +799,9 @@
     try:
       file_content = utils.ReadFile(filename)
     except EnvironmentError as err:
-      raise errors.HypervisorError("Failed to load Xen config file: %s" % err)
+      ## temporarily fix xen migration with missing config
+      file_content = ""
+      #raise errors.HypervisorError("Failed to load Xen config file: %s" % err)

     return file_content

@@ -1208,6 +1210,7 @@
     @return: content of the xen config file

     """
+    ##TODO: we need to create a current config file if it does not exist
     return self._ReadConfigFile(instance.name)

   def _UseMigrationDaemon(self, hvparams):
@@ -1359,7 +1362,8 @@
       # of usable SSH keys as of 2.13
       args.extend([
         "-s", constants.XL_SOCAT_CMD % (target, port),
-        "-C", self._ConfigFileName(instance_name),
+        ## temporarily fix xen migration
+        #"-C", self._ConfigFileName(instance_name),
         ])

     else: