tests: add configuration file test via RPC

This test checks the following things:

 * Does configuration file parsing work at all.
 * Does the parser detect wrong options.
 * Does the configuration file work via RPC.
 * Do the configuration file options not overwrite the RPC settings in
   the default setup.
 * Is it possible to tell CRIU to prefer the configuration file via RPC.

Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>