travis-ci: collect logs from cmocka tests
    
    When 'make check' is run, automake produces logs for each test to be ran.
    Collect all the logs from the tests.
    
    Also prepare the template to quickly enable use of gdb with traceback
    in case a test is crashing. To use it, add LOG_COMPILE definition to
    the 'make' line.
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>