load_policy changed the old model

[GHNSL]

in core_enforcer.py
def load_policy(self):
"""reloads the policy from file/database."""
need_to_rebuild = False
new_model = copy.copy(self.model)
new_model.clear_policy()

new_model.clear_policy() will change the policy in self.model, becourse it's a shallow copy

[casbin-bot]

@techoner @Nekotoxin

[hsluoyz]

@leeqvip @Xhy-5000