In aosp/1581143 , we banned generation of SPL downgrade OTAs. However,
caller of OTA script can still force an SPL downgrade OTA by passing
--spl_downgrade flag. If this flag is specified, we propagate it to OTA
metadata so that GOTA server can properly honor this flag.
Test: th
Change-Id: Ic8cdc850d2210f4149ad9121fa4ed2e5a4f59bcc
Sometimes tests are being run by executing python -m unittest *.py. In
that case, invocation will fail due to missing ota_metadata_pb2, which
is auto generated from ota_metadata.proto(added in recent change).
Bug: 166718341
Test: unzip otatools.zip and python releasetools/test_utils.py
Change-Id: I597c7ef6dbd8e46ccde020b3122cc38a8df28dc9