prevent DscpPolicyTracker from printing big scary exception stack

when the program is missing due to too old kernel.
Program presence is already enforced by CRITICAL annotation and bpfloader.

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ic5f53636c833e65c611a7b8069f28c088c249158
4 files changed