runner: Kill a program under test by time-out

If a program under test get frozen, the test should finish and report about its
failure.
In such cases the runner waits for 10 minutes until the program ends its
execution. After this time-out the program will be terminated and the test will
be marked as failed.

For current limitation of test image size to 10 MB as a maximum an execution of
each command takes about several seconds in general, so 10 minutes is enough to
discriminate freeze, but not drastically increase an overall test duration.

Signed-off-by: Maria Kustova <maria.k@catit.be>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
