fix CTS tests

Exclude package com.android.cts.priv.ctsshim from signature checks.
This package can be signed with a known signature.

Bug: 28653061
Change-Id: I2eea4e9fb7a772155be09f896fd26e991a84fd66
diff --git a/tests/tests/security/src/android/security/cts/PackageSignatureTest.java b/tests/tests/security/src/android/security/cts/PackageSignatureTest.java
index 6024a4b..3d63b51 100644
--- a/tests/tests/security/src/android/security/cts/PackageSignatureTest.java
+++ b/tests/tests/security/src/android/security/cts/PackageSignatureTest.java
@@ -108,7 +108,10 @@
             "android.core.tests.libcore.package.libcore",
             "android.core.tests.libcore.package.org",
             "android.core.tests.libcore.package.sun",
-            "android.core.tests.libcore.package.tests"
+            "android.core.tests.libcore.package.tests",
+
+            // Test package to verify upgrades to privileged applications
+            "com.android.cts.priv.ctsshim"
 
             ));