Improve scrolling cache

Scrolling cache helps make short scrolls/flings smooth but will
cause stutter when long flings are made. This patch disables
scrolling cache when long flings are made.

This patch also fixes a related bug where scrolling cache will
not be enabled properly when transitioning from flinging to scrolling.

Patch Set 2: Calculate threshold based on maximum velocity (Sang Tae Park)

Credits: Pawit Pornkitprasan

Change-Id: I1fdbaad92263c9f983a32900e74eba1f0367902b
Signed-off-by: Arham Jamal <arhamjamal@gmail.com>
Clear the scan list when an empty list is received

When the framework receives an empty scan list from supplicant, it does
not clear the local list. So the UI will continue to show the previous
scan list even when there are no APs around. So clear the local list,
when an empty list is received.

CRs-Fixed: 552212
Change-Id: I8715bc31ce0df7bd54c96fcf7d7b73592429f12a
Close sockets on wpa_supplicant termination.

Framework does not close the sockets on supplicant
termination, leading to leakage of file descriptors.

Thus close the socket on supplicant termination.

Change-Id: I50aefc6d60b3794288564f403a42258442e224df
CRs-Fixed: 576276