l10nupdate: aquire scap lock before changing files
Prevent occasional file update wars between the cron'd l10nupdate
process and manual deployments by respecting the /var/lock/scap lock
file. l10nupdate will wait on an exclusive lock of /var/lock/scap before
changing the php-*/cache/l10n CDB and json files. The lock has to be
released before running scap sync-l10n or scap's internal locking will
fail.
Bug: T72752
Change-Id: I2a51093686edd1aaeb3ea52d2b986cc62b49d762