pw_software_update: OpenAndVerify() should fail clean
pw_software_update: OpenAndVerify() should fail clean

Leave blobstore reader closed when OpenAndVerify() fails.

Change-Id: Ia1436980761be26609c98e4523d95bf0b2131ff3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/88926
Pigweed-Auto-Submit: Ali Zhang <101974175ff73f104389b21e58229a7713cff21f@google.com>
Reviewed-by: Yecheng Zhao <858a3f9ab0d064c70af0dcd6105b38f356960c6a@google.com>
Reviewed-by: Tim Knodel <1e62a3f275c1072686aa617cda5c871b3a74c148@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed