Adjust bpf_existence_test.cpp for dscp_policy 5.15+ change

The minimal required kernel version was changed in:
  https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2141233
  'DscpPolicy Move to kernel 5.15'

Bug: 235559605
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ibc1b1410155a2279ed84ec4cdc475f65dc61b077
(cherry picked from commit b73da9658c705ba3eaf81895bff32177890f4391)
Merged-In: Ibc1b1410155a2279ed84ec4cdc475f65dc61b077
1 file changed