Initialize logging function and log_level for libsoccr.
Otherwise all soccr messages are skipped.

travis-ci: success for libsoccr debug/info messages
Reported-by: Adrian Reber <adrian@lisas.de>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>