Don't remove wifi preferences when updating AP to avoid GC.

Bug: 30870531

Removing wifi preferences every time will force update create a new set
of preferences, which leads to higher chance of GC.

Change-Id: Ifea2f63a3b54fa0d5861fb34a348d81e99bcab68
(cherry picked from commit 9d031f2fbce4cc525e4d5a5598e9c9d1813c2ce2)
1 file changed