Increase reliability of Teleservice tests.

Many flakes are seen due to calls to `unbindService` resulting in an
`UnSupportedOperationException`; this is due to the fact that
`MockContext` throws for that method.

Test: This is a test fix:
Flag: NONE test only fix
Fixes: 379279946
Change-Id: I6bcf344a42c1a60944c2a7431ba002d9b9057a2c
diff --git a/tests/src/com/android/TestContext.java b/tests/src/com/android/TestContext.java
index a684ef5..2b35473 100644
--- a/tests/src/com/android/TestContext.java
+++ b/tests/src/com/android/TestContext.java
@@ -27,6 +27,7 @@
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.content.ServiceConnection;
 import android.content.pm.PackageManager;
 import android.os.Binder;
 import android.os.Handler;
@@ -274,6 +275,11 @@
         }
     }
 
+    @Override
+    public void unbindService(ServiceConnection conn) {
+        // Override the base implementation to ensure we don't crash.
+    }
+
     public void grantPermission(String permission) {
         synchronized (mPermissionTable) {
             if (permission == null) return;