[CrOS Tether] Filter BLE discovery to LE devices only.

Instant Tethering only uses BLE connections. This filter was not
previously used due to a potential workaround which had been resolved
(see https://crbug.com/759090).

TBR=khorimoto@google.com

(cherry picked from commit a29a5d737d9d8a2aa4c1241c01d7157bb61d3ec2)

Bug: 759091, 672263
Change-Id: I161efd638f683d21596e445a5f1db2f90a838e75
Reviewed-on: https://chromium-review.googlesource.com/919426
Reviewed-by: Rahul Chaturvedi <rkc@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#537140}
Reviewed-on: https://chromium-review.googlesource.com/927342
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#513}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
2 files changed