Recently some testcases have been failing in travis because of a warning
related to the use of an L3 device (OpenVZ specific) inside the workers.

To get travis tests working again we can move to the newer container
infrastructure: this commit does that.

The disadvantage is that there's no sudo access anymore, but we can
install packages with the apt plugin, and we shouldn't use root for
anything else

Also, since we're building DPDK with vhost-user (not vhost-cuse),
libfuse-dev is not needed anymore.

[back ported to branch-2.4 by azhou.ovn.org]
Upstream: e88b97cb



branch-2.4 travis builds are broken due to travis-ci infrastructure
changes. Move to use the newer container infrastructure to
restore builds. Note, libfuse-dev is required for branch-2.4 builds.

Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>
CC: Joe Stringer <joestringer@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: Andy Zhou <azhou@ovn.org>