ExpandHelper: Improve one finger expanding forced handling

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.

Change-Id: I639eb94c44763ce480d4e2f22cdd91c53e4328b1
Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

Conflicts:
	packages/SystemUI/src/com/android/systemui/ExpandHelper.java