admin: make data linter exit 1 on error

'data_admin.py lint' detects issues in the data.yaml file, make it exit
1 as to easily detects there is an error.

Change-Id: Ia7c9e04a6ff6f776ca1400f472f68a5dffa1b03e
Merge "admin: make data linter exit 1 on error" into production