bluetooth: find servod config path

Remove the hardcodes of python2.7. Find the servod config path
dynamically.

BUG=b:159192174
TEST=Run AVL tests.

Change-Id: I3396468091ad878f0ceee1781ad935bc43451eac
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/chameleon/+/2831452
Reviewed-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Commit-Queue: Shyh-In Hwang <josephsih@chromium.org>
Tested-by: Shyh-In Hwang <josephsih@chromium.org>
1 file changed