check_result: Correctly check the __extend__ state.
check_result: Correctly check the __extend__ state.

https://github.com/saltstack/salt/issues/42512

check_state_result() is expecting each highstate item to be a dict, but
states using extend are lists.

Conflicts:
  - salt/utils/state.py

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt