Initialize HookCaller._call_history to None instead of using hasattr
Initialize HookCaller._call_history to None instead of using hasattr

hasattr is slow, can't be typed properly, and makes the code harder to
understand.

RonnyPfannschmidt/pluggy,RonnyPfannschmidt/pluggy,hpk42/pluggy,pytest-dev/pluggy,pytest-dev/pluggy