RPC server: add function get_control_file_from_test().

Add function get_control_file_from_test() to get the content of a Control File
from a specific test id.

In Test class (models.py) create method get_control_file().
Update INTERFACE_VERSION to version 2014.1.17.

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