Correct the namespace of DeviceConfig in VpnTest

The namespace used in production code is NAMESPACE_TETHERING, not
NAMESPACE_CONNECTIVITY.

Test: atest com.android.cts.net.HostsideVpnTests
Change-Id: I0f31176c521e2a877a964c2bbe6f387c4e71352a
diff --git a/tests/cts/hostside/app/src/com/android/cts/net/hostside/VpnTest.java b/tests/cts/hostside/app/src/com/android/cts/net/hostside/VpnTest.java
index 73a6502..cd3b650 100755
--- a/tests/cts/hostside/app/src/com/android/cts/net/hostside/VpnTest.java
+++ b/tests/cts/hostside/app/src/com/android/cts/net/hostside/VpnTest.java
@@ -1175,8 +1175,8 @@
 
         final String origMode = runWithShellPermissionIdentity(() -> {
             final String mode = DeviceConfig.getProperty(
-                    DeviceConfig.NAMESPACE_CONNECTIVITY, AUTOMATIC_ON_OFF_KEEPALIVE_VERSION);
-            DeviceConfig.setProperty(DeviceConfig.NAMESPACE_CONNECTIVITY,
+                    DeviceConfig.NAMESPACE_TETHERING, AUTOMATIC_ON_OFF_KEEPALIVE_VERSION);
+            DeviceConfig.setProperty(DeviceConfig.NAMESPACE_TETHERING,
                     AUTOMATIC_ON_OFF_KEEPALIVE_VERSION,
                     AUTOMATIC_ON_OFF_KEEPALIVE_ENABLED, false /* makeDefault */);
             return mode;
@@ -1216,7 +1216,7 @@
 
             runWithShellPermissionIdentity(() -> {
                 DeviceConfig.setProperty(
-                                DeviceConfig.NAMESPACE_CONNECTIVITY,
+                                DeviceConfig.NAMESPACE_TETHERING,
                                 AUTOMATIC_ON_OFF_KEEPALIVE_VERSION,
                                 origMode, false);
                 mCM.setTestLowTcpPollingTimerForKeepalive(0);