Correct error message for "create server --wait"

Error message should say "Error creating server" and not "unshelving".

Change-Id: I49dc6160f47a13d38128b3da1ba16437bd089c86
Closes-Bug: #2048896

Author: rubasov

openstackclient/compute/v2/server.py

@@ -2005,9 +2005,7 @@ def _match_image(image_api, wanted_properties):
             ):
                 self.app.stdout.write('\n')
             else:
-                msg = (
-                    _('Error unshelving server: %s') % parsed_args.server_name
-                )
+                msg = _('Error creating server: %s') % parsed_args.server_name
                 raise exceptions.CommandError(msg)
 
         details = _prep_server_detail(compute_client, image_client, server)