Intitialize AcceptableLeftDistance with NUM_OP-1.

Originally, on receiving any report from app AcceptableLeftDistance was decreasing below
NUM_OP. After changes introduced in ag/12060128, AcceptableLeftDistance doesn't always
change on report receipt.

Fix: 161451424
Test: atest RuntimeMessageCollectionTest
Change-Id: Id9a066d9efb16a60b2d68c78fb06bbd549c83e40