contrib/test/int: allow to configure test timeout
contrib/test/int: allow to configure test timeout

Changing runtime may change test execution time. This is especially true
for kata-containers runtime which at present will require more time to run.
Allow to specify a different deadline for test execution by setting the
int_test_timeout var.

Signed-off-by: Francesco Giudici <b8db29a919912789b3151b2e6d7b4adf2efbc22b@redhat.com>

kubernetes-incubator/cri-o,kubernetes-incubator/cri-o,nalind/cri-o,nalind/cri-o,kubernetes-incubator/cri-o,kubernetes-incubator/ocid,nalind/cri-o,kubernetes-incubator/ocid,kubernetes-incubator/ocid,kubernetes-incubator/cri-o