travis: stop using container based envs

The Travis container based envs are deprecated:

  https://docs.travis-ci.com/user/reference/trusty/

  "Container-based infrastructure is currently being deprecated.
   Please remove any sudo: false keys in your .travis.yml file
   to use the default fully-virtualized Linux infrastructure
   instead."

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

.travis.yml

@@ -1,8 +1,4 @@
-# The current Travis default is a container based 14.04 Trust on EC2
-# Additional builds with specific requirements for a full VM need to
-# be added as additional matrix: entries later on
 
-sudo: false
 dist: trusty
 language: c
 python:
@@ -255,6 +251,5 @@ matrix:
     - env:
         - CONFIG="--disable-system --disable-docs"
         - TEST_CMD="make -j3 check-tcg"
-      sudo: required
       dist: trusty
       compiler: gcc