Remove test_utils::RecursiveUnlinkDir().

This test-only function has an equivalent implementation in libcrhome
so we remove it from update_engine and use the library version instead.

Bug: None
Test: FEATURES=test emerge-link update_engine

Change-Id: I3027c879d40461dbdf8b52dd1b65da0240549c9c
diff --git a/fake_p2p_manager_configuration.h b/fake_p2p_manager_configuration.h
index 6874efb..8563d6e 100644
--- a/fake_p2p_manager_configuration.h
+++ b/fake_p2p_manager_configuration.h
@@ -25,6 +25,7 @@
 #include <vector>
 
 #include <base/logging.h>
+#include <base/files/file_util.h>
 #include <base/strings/string_util.h>
 #include <base/strings/string_number_conversions.h>
 
@@ -39,7 +40,8 @@
   }
 
   ~FakeP2PManagerConfiguration() {
-    if (p2p_dir_.size() > 0 && !test_utils::RecursiveUnlinkDir(p2p_dir_)) {
+    if (p2p_dir_.size() > 0 &&
+        !base::DeleteFile(base::FilePath(p2p_dir_), true)) {
       PLOG(ERROR) << "Unable to unlink files and directory in " << p2p_dir_;
     }
   }