drop_materialized_views is new support and needs to be
conditional on finding a recent version currently installed.
Add output to show what the maintainer script is doing.

Some migrations can alter fields which already have a
materialized view in the database. Existing code already
refreshes all materialized views, so ensure that views are
dropped ahead of the sync, retaining creation in the refresh.

Ensure that at least some operations test the installed server.

Avoid #869098.
Drop Antonion from uploaders upon request.

Change ownership of devices directory to lavaserver.

See https://bugs.linaro.org/show_bug.cgi?id=3020

lava-dev needs to update the python-sphinx dependency to match
the build-depends on lava-server.