Make BaseAppSecurityTest abstract.

This class has no @Test methods, which causes CTS to fail if it tries to run it.

Test: m -j CtsAppSecurityHostTestCases CtsDocumentClient && \
      cts-tradefed run commandAndExit cts-dev -m CtsAppSecurityHostTestCases \
      -t android.appsecurity.cts.ScopedDirectoryAccessTest
Bug: 69981990

Change-Id: I401260580a2997687d8d779c9491c2b7b7398373
diff --git a/hostsidetests/appsecurity/src/android/appsecurity/cts/BaseAppSecurityTest.java b/hostsidetests/appsecurity/src/android/appsecurity/cts/BaseAppSecurityTest.java
index 26065ca..5e2a97b 100644
--- a/hostsidetests/appsecurity/src/android/appsecurity/cts/BaseAppSecurityTest.java
+++ b/hostsidetests/appsecurity/src/android/appsecurity/cts/BaseAppSecurityTest.java
@@ -28,7 +28,7 @@
 /**
  * Base class.
  */
-public class BaseAppSecurityTest extends BaseHostJUnit4Test {
+abstract class BaseAppSecurityTest extends BaseHostJUnit4Test {
 
     /** Whether multi-user is supported. */
     protected boolean mSupportsMultiUser;