dscpPolicy.c - cache result-less lookups as well am: d7b92c03e9

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2166371

Change-Id: I3c219907039da5aeb03d2bc8346db36d93917e3b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>