Fix the NPE caused when the battery condition fails. To make this CTS testable, change the battery check mechanism and force DevicePolicyConstants to reload when the device_policy_constants global settings are modified. Change-Id: I59d4630a6dd2d1b52f1adb1da4238ee53c20c0e6 Fixes: 112076619 Test: atest com.android.cts.devicepolicy.DeviceOwnerTest#testInstallUpdate