Reduce unnecessary callbacks in AppOpsService.

When AppOpsCheckingServiceImpl#setUidMode returns true, many watchers will receive callbacks. When the system is busy, it will cause the Handler message queue to accumulate, leading to serious problems such as untimely broadcast distribution. Therefore, we reduce some callbacks when the op mode does not really change.

Change-Id: Id010dab1392713cc0ba8982ab42e857d3ce8151d
Merged-In: I41d79fdba0dcdc56a287082e22663fbc85998fb2