Don't attempt to enable rate-limiting before T.

Rate-limiting cannot work because the BPF program is in the
mainline version of netd.c, which is placed into net_shared
and thus cannot run pre-T.

Disable it entirely to ensure no impact on S.

Test: atest ConnectivityCoverageTests:com.android.server.ConnectivityServiceTest on AOSP
Test: atest ConnectivityCoverageTests:com.android.server.ConnectivityServiceTest on S
Change-Id: I47521a100f8287ecdece25e810db8f3cade46778
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index ab78104..6c45ab4 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -10699,6 +10699,9 @@
     }
 
     private boolean canNetworkBeRateLimited(@NonNull final NetworkAgentInfo networkAgent) {
+        // Rate-limiting cannot run correctly before T because the BPF program is not loaded.
+        if (!SdkLevel.isAtLeastT()) return false;
+
         final NetworkCapabilities agentCaps = networkAgent.networkCapabilities;
         // Only test networks (they cannot hold NET_CAPABILITY_INTERNET) and networks that provide
         // internet connectivity can be rate limited.