Camera: Don't try to set focus/metering areas when none exist

Avoid calling the set methods when the areas are null, this causes
issues with some camera HALs

Change-Id: Iea6efbe113e1c87f22c891bf8a9cd47bc2c1cb22
Camera: Do not start autofocus when snapshot is in progress.

(cherry picked from commit 9fbccbe5bad2249e13a86581ecbd1e68810a0e90)

Change-Id: Id28c90b43ce33702d9c421e9a3b19d4502b77609