Fix directory recursion in FileSystemPermissionTest

FileSystemPermissionTest.testAllBlockDevicesAreSecure() was missing
the check for symbolic links, so add it.

Change-Id: I821e6806e2ae8f7a4b472ab2f2d4d1e17616f188
diff --git a/tests/tests/permission/src/android/permission/cts/FileSystemPermissionTest.java b/tests/tests/permission/src/android/permission/cts/FileSystemPermissionTest.java
index 92f3e53..ec4fe3f 100644
--- a/tests/tests/permission/src/android/permission/cts/FileSystemPermissionTest.java
+++ b/tests/tests/permission/src/android/permission/cts/FileSystemPermissionTest.java
@@ -665,6 +665,12 @@
     getAllInsecureBlockDevicesInDirAndSubdir(File dir) throws Exception {
         assertTrue(dir.isDirectory());
         Set<File> retval = new HashSet<File>();
+
+        if (isSymbolicLink(dir)) {
+            // don't examine symbolic links.
+            return retval;
+        }
+
         File[] subDirectories = dir.listFiles(new FileFilter() {
             @Override public boolean accept(File pathname) {
                 return pathname.isDirectory();