Swith to coreutils timeout

Swith to coreutils timeout

juju is not correctly stopped when no internet.

https://build.opnfv.org/ci/job/functest-ovn-opnfv-functest-vnf-jerma-juju_epc-run/21/console
root           1       0  0 Apr04 ?        00:00:06 /usr/bin/python3.7 /usr/bin/run_tests -t juju_epc -r -p
root         139       1  0 Apr04 ?        00:00:03 [juju] <defunct>
root         141       1  0 Apr04 ?        00:00:00 [timeout] <defunct>

Change-Id: Id06c6e829ab8a992107f655aac6ec4539e292d82
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
(cherry picked from commit cda22d7db0bcca380e1caef76e171cd7753b6221)