Add shell command to query Restricted Mode state

This will be used in the CTS test to query the state of the Restricted
Mode.

Test: adb shell cmd netpolicy get restricted-mode
Bug: 170323671
Bug: 175281879
Change-Id: Ic25b5835d48a4b54eb9f2b4817244651ea09bd60

services/core/java/com/android/server/net/NetworkPolicyManagerService.java

@@ -3864,6 +3864,13 @@ public class NetworkPolicyManagerService extends INetworkPolicyManager.Stub {
         }
     }
 
+    @VisibleForTesting
+    boolean isRestrictedModeEnabled() {
+        synchronized (mUidRulesFirstLock) {
+            return mRestrictedNetworkingMode;
+        }
+    }
+
     /**
      * updates restricted mode state / access for all apps
      * Called on initialization and when restricted mode is enabled / disabled.

services/core/java/com/android/server/net/NetworkPolicyManagerShellCommand.java

@@ -119,6 +119,8 @@ class NetworkPolicyManagerShellCommand extends ShellCommand {
         switch(type) {
             case "restrict-background":
                 return getRestrictBackground();
+            case "restricted-mode":
+                return getRestrictedModeState();
         }
         pw.println("Error: unknown get type '" + type + "'");
         return -1;
@@ -255,6 +257,13 @@ class NetworkPolicyManagerShellCommand extends ShellCommand {
         return listUidList("App Idle whitelisted UIDs", uids);
     }
 
+    private int getRestrictedModeState() {
+        final PrintWriter pw = getOutPrintWriter();
+        pw.print("Restricted mode status: ");
+        pw.println(mInterface.isRestrictedModeEnabled() ? "enabled" : "disabled");
+        return 0;
+    }
+
     private int getRestrictBackground() throws RemoteException {
         final PrintWriter pw = getOutPrintWriter();
         pw.print("Restrict background status: ");