ExpandHelper: Improve one finger expanding forced handling

This commit was RE-committed by @Namja in Triangles

Instead of force returning false if view is null, setup a boolean
to force it with custom views like hover. Cherry-picked from CM.

Also request disallow intercept on drag started.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Conflicts:
	packages/SystemUI/src/com/android/systemui/ExpandHelper.java
	packages/SystemUI/src/com/android/systemui/statusbar/notification/HoverLayout.java

Change-Id: Iee257247862740096b180e38ebf01d1036c2c8e6