job command: Add option --from-test-number.

Add option --from-test-number to allow create a job from a test
registered on the autotest server. Example:

    ./scripts/arcli test --list | grep 'Sleeptest'
    4   Server Sleeptest
    57  Sleeptest
    ./scripts/arcli job --add --name t57 --machine vm-fedora \
                        --from-test-number 57

Signed-off-by: Ruda Moura <rmoura@redhat.com>
Merge pull request #3 from ruda/add_job_from_test_id_alternative

job command: Add option --from-test-number.