created FORCE_DEVICE_POLICY_MANAGER_LOG and CLEAR_FREEZE_PERIOD

Created the following new permissions and granted it to shell:
* FORCE_DEVICE_POLICY_MANAGER_LOG: will be used to expose
DPM#forceNetworkLogs and DPM#forceSecurityLogs as TestAPIs.
* CLEAR_FREEZE_PERIOD: will be used to expose
DPM#clearSystemUpdatePolicyFreezePeriodRecord as a TestAPI.

Bug: 180500227
Test: atest PermissionPolicyTest#platformPermissionPolicyIsUnaltered
Change-Id: I8a2a49aa45704d8991e9cf3689b5259442fb1db3