scripts/arcli: simple magic for running scripts within the source tree

This should improve user's experience when running arcli out of a
source tree checkout.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
user and label commands: accept action 'list full'

For user and label commands, accept the action to list all information.
Protect listing and printing tables from empty values.

Signed-off-by: Ruda Moura <rmoura@redhat.com>