UPSTREAM: lib/uuid: Make bt_uuid_to_string always use the same format

The convention has been to use 128 Bits UUID strings so other types must
be converted first.
(cherry picked from commit 0a4ac85042a1cdcfedf4cb782edc9bd1c814f3a7)

BUG=chrome-os-partner:48794
TEST=manually

Change-Id: I086c751ab6dc129013202955b845c03a4527c364
Reviewed-on: https://chromium-review.googlesource.com/325183
Commit-Ready: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
1 file changed