ci,build: un-dockerize bionic build

Travis-CI should have some Bionic docker images. Switch to those.
Using these should be slightly less overhead.

Ref: https://docs.travis-ci.com/user/reference/bionic/

Signed-off-by: Alexandru Ardelean <[email protected]>

Author: commodo

.travis.yml

@@ -66,9 +66,8 @@ matrix:
         - OS_VERSION=7
         - EXTRA_SSH=-oHostKeyAlgorithms=+ssh-dss
     - os: linux
+      dist: bionic
       env:
-        - OS_TYPE=ubuntu_docker
-        - OS_VERSION=bionic
         - EXTRA_SSH=-oHostKeyAlgorithms=+ssh-dss
     - compiler: "gcc"
       os: osx