Enabled state shouldn't effect children.

Accidentally had enabled state effecting children in setFlags
which would sometimes cause child views to lose focus when their
parents changed enabled state.

Bug: 70718160
Test: Trello app issue fixed.
      Added regression test View_FocusHandlingTest#testEnabledHandling
Change-Id: Idcd672d833969d11b235357230ce2f560dd90c43