mesh: misc error logging cleanups

This demotes 2 error level logging to info level:
1. "Using interface %s with hwaddr" is just information. This is in the
  normal code path without any error condition.
2. rmdir /var/runwpa_supplicant will always fail as only root has write
  access to /var/run. So the rmdir error logging is expected.
And don't call ieee802_11_set_beacons() that is not applicable to mesh.

BUG=b:31156577
TEST=manually on gale

Change-Id: I6776fd0c6da28a5ea01b85b9d5c4ee85b5ebfd9e
Reviewed-on: https://chromium-review.googlesource.com/417128
Commit-Ready: Julan Hsu <julanhsu@google.com>
Tested-by: Julan Hsu <julanhsu@google.com>
Reviewed-by: Srinivasa duvvuri <sduvvuri@chromium.org>
4 files changed