Fix races in ConfirmPassword/Pattern

- Add a CheckLockResultTracker to track result of async lock check so that
  it can finish on configuration change;
- Let the pending lock check finish and ignore subsequent check requests;
- Add a mDisappearing flag to prevent running disappear animation
  multiple times;
- Check whether activity is still active after disappear animation
  before setting result and finishing it;
- Remove no longer used mNumWrongConfirmAttempts;

Bug:23190499
Change-Id: If1784d3d1fcc152ac06137b12748b9def5726692