Disable phrase rescore if rescore window is 0

Change-Id: Ie91cf5e625e5f2d1f126b443d6c16983ea50cda0
(cherry picked from commit 99890ad3aade86614dc7ad06b3cf9b7a31ee0176)
Merge "Disable phrase rescore if rescore window is 0" into wmf/1.24wmf20