Add exported flag to exposed test runtime receiver

Android T allows apps to declare a runtime receiver as not exported
by invoking registerReceiver with a new RECEIVER_NOT_EXPORTED flag;
receivers registered with this flag will only receive broadcasts from
the platform and the app itself. However to ensure developers can
properly protect their receivers, all apps targeting a future
platform release and registering a receiver for non-system
broadcasts must specify either the exported or not exported flag
when invoking #registerReceiver; if one of these flags is not
provided, the platform will throw a SecurityException. This commit
updates all the exposed receiver with the RECEIVER_EXPORTED flag
to maintain the existing behavior for this test.

Bug: 234659204
Test: atest CtsHostsideNetworkTests:com.android.cts.net.HostsideVpnTests
Change-Id: I61b3ee109cf37545918f03daf1fbe1ea90157002
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 5f032be..8c18a89 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
@@ -38,6 +38,7 @@
 import static com.android.compatibility.common.util.SystemUtil.runWithShellPermissionIdentity;
 import static com.android.networkstack.apishim.ConstantsShim.BLOCKED_REASON_LOCKDOWN_VPN;
 import static com.android.networkstack.apishim.ConstantsShim.BLOCKED_REASON_NONE;
+import static com.android.networkstack.apishim.ConstantsShim.RECEIVER_EXPORTED;
 import static com.android.testutils.Cleanup.testAndCleanup;
 import static com.android.testutils.DevSdkIgnoreRuleKt.SC_V2;
 
@@ -1550,8 +1551,9 @@
         final DownloadManager dm = context.getSystemService(DownloadManager.class);
         final DownloadCompleteReceiver receiver = new DownloadCompleteReceiver();
         try {
+            final int flags = SdkLevel.isAtLeastT() ? RECEIVER_EXPORTED : 0;
             context.registerReceiver(receiver,
-                    new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
+                    new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE), flags);
 
             // Enqueue a request and check only one download.
             final long id = dm.enqueue(new Request(