Fix QS expansion weirdness

- Fix that the clock/avatar could get too large.
- Fix QS collapsing when on Keyguard and scroll view is scrolled
- Fix that clock/avatar didn't grow after a layout when expanding
- Fix flicker in header when overexpanding the panel
- Fix flicker from QS panel when it changes size
- Fix that scroll view still was scrolled after collapsing QS

Bug: 16869692
Bug: 16894194
Change-Id: Ic0f89ab860979db4d0438007b4d0d044d3e8c4ae