sign_cr50_firmware: use sanitized manifest file
sign_cr50_firmware: use sanitized manifest file

This patch makes sure that Cr50 manifest included in the builder
produced tarball is stripped to remove the comments before it is given
to jq for processing.

Also a little clean up.

BRANCH=none
BUG=b:74100307
TEST=tested as described in the next patch.

Change-Id: I4852fea7c21752c45fcfe4cc60d45f264f142bab
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1529387
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot