Don't orphan footers with transient state

Bug #8725945

Selecting text in an EditText causes the View to have transient
state. This would in turn cause the View to be removed from its
ListView parent. When removed, the EditText would lose its
AttachInfo, causing all sorts of problems. Headers and footers
must not be removed, only detached. This is the part of the fix
in AbsListView.

Fixing AbsListView triggered a second bug: when a View is removed
from the Window manager, it would keep its parent assigned, thus
making it impossible to add it again to the window manager. When
a ViewRootImpl goes through doDie(), it must set its content view's
parent to null to properly cleanup.

Change-Id: I0489daa74f8f7fcf85526f0928f8925ec30d4f42