Can't set_rules without using config file in policy

[Shuangtai Tian]

In the policy modules, the load_rules will always load the rules from the cache or config file when check the policy.
So the set_rules doesn't work. and the Enforcer init with rules also does not work.

for example:
   ENFORCER = policy.Enforcer()
   ENFORCER.set_rules({'a': 'b'})
   self.assertEqual(self.enforcer.rules, {'a': 'b'}) --- success
   action = 'a'
   creds = {'roles': ''}
   self.assertEqual(self.enforcer.enforce(action, {}, creds), True) -- failed

the last assert failed just because in the enforce() would call load_rules() and rewrote the rules using the config file (policy.json), the file is modified.
https://github.com/openstack/oslo-incubator/blob/master/openstack/common/policy.py#L228

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/72848

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/72848
Committed: https://git.openstack.org/cgit/openstack/oslo-incubator/commit/?id=15722f1702bc8c2fb2c93261a8d395f69bc4df1d
Submitter: Jenkins
Branch: master

commit 15722f1702bc8c2fb2c93261a8d395f69bc4df1d
Author: Shuangtai Tian <email address hidden>
Date: Wed Feb 12 14:09:53 2014 +0800

    Adds a flag to determine whether to reload the rules in policy

    Initing a Enforcer class with rules can not set rules, because the policy
    file is modified , the load_rules always try to load the rules from the cache
    or config file when checks the policy. This patch adds a flag to determine
    whether to reload the rules from policy file.

    Closes-Bug: #1279198

    Change-Id: Ife84189be4b86a3ee90da4539ff2dbed125be23d