findNetworkStackApk returns an array of files (2/n)

This change handles the case of split APKs. All files starting with
"NetworkStack" will be returned as split APKs.

See b/159978937#comment6. NetworkStack is changed from a single APK to
split APKs. We need this change for install to succeed.

Bug: 159978937
Test: atest NetworkStagedRollbackTest
Change-Id: I20f5fee08ea208ba4dc7711d82a1718239c647c2
diff --git a/tests/RollbackTest/RollbackTest/src/com/android/tests/rollback/NetworkStagedRollbackTest.java b/tests/RollbackTest/RollbackTest/src/com/android/tests/rollback/NetworkStagedRollbackTest.java
index 42b0c60..314e952 100644
--- a/tests/RollbackTest/RollbackTest/src/com/android/tests/rollback/NetworkStagedRollbackTest.java
+++ b/tests/RollbackTest/RollbackTest/src/com/android/tests/rollback/NetworkStagedRollbackTest.java
@@ -61,11 +61,12 @@
     private static final TestApp NETWORK_STACK = new TestApp("NetworkStack",
             getNetworkStackPackageName(), -1, false, findNetworkStackApk());
 
-    private static File findNetworkStackApk() {
+    private static File[] findNetworkStackApk() {
         for (String name : NETWORK_STACK_APK_NAMES) {
             final File apk = new File("/system/priv-app/" + name + "/" + name + ".apk");
             if (apk.isFile()) {
-                return apk;
+                final File dir = new File("/system/priv-app/" + name);
+                return dir.listFiles((d, f) -> f.startsWith(name));
             }
         }
         throw new RuntimeException("Can't find NetworkStackApk");