releasetools: Move recovery-two-step.img to OTA/.

It used to be packed at IMAGES/recovery-two-step.img, but to serve OTA
purpose only.

Test: `m dist` with a non-A/B target. Check the file in the generated
      target_files.zip.
Test: Create two-step package. Check that recovery-two-step.img is used.
Change-Id: Iec6a73c682e0f844cd8c0b758c9470fa35dd15d8
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index 435e7f2..d189499 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -257,7 +257,10 @@
     if verity_key is None:
       verity_key = info_dict['verity_key'] + '.x509.pem'
     for image in ('boot.img', 'recovery.img', 'recovery-two-step.img'):
-      image_path = os.path.join(input_tmp, 'IMAGES', image)
+      if image == 'recovery-two-step.img':
+        image_path = os.path.join(input_tmp, 'OTA', image)
+      else:
+        image_path = os.path.join(input_tmp, 'IMAGES', image)
       if not os.path.exists(image_path):
         continue