Make sync-common update l10n cdb files by default

Deployers (and puppet) mostly assume that sync-common is all that is
needed to update a host with the deploy master. Nobody remembers that
you now have to run scap-rebuild-cdbs too. Fix this by making the
default behavior of sync-common include updating cdbs from the synced
json files. `scap` and friends will call as
`sync-common --no-update-l10n ...` to preserve existing split workflow.

Bug: 69792
Change-Id: I634fe0a19b909cfc84925e4661ee2bc320359095