scripts: pushimage: avoid reparsing recovery instructions

image_type is re-assigned to RECOVERY when None, so will never be
None here, and the RECOVERY instructions are explicitly parsed before
parsing the image_type's instructions, so skip the image_type
instructions when it's RECOVERY.

BUG=None
TEST=CQ

Change-Id: Iecdd88f804d069649b735dc559cd32c96dc72599
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4774773
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
diff --git a/scripts/pushimage.py b/scripts/pushimage.py
index 382ea30..71028a5 100644
--- a/scripts/pushimage.py
+++ b/scripts/pushimage.py
@@ -98,7 +98,7 @@
         with open(input_insns, encoding="utf-8") as fp:
             config.read_file(fp)
 
-        if image_type is not None:
+        if image_type != constants.IMAGE_TYPE_RECOVERY:
             input_insns = self.GetInsnFile(image_type)
             if not os.path.exists(input_insns):
                 # This type doesn't have any signing instructions.