travis: update configuration

Update the set of Go versions (and use 1.x to always test the latest
release), as well as making the cgroupv2 tests allowable failures (the
vagrant setup seems to break pretty often, causing flaky failures).

Signed-off-by: Aleksa Sarai <asarai@suse.de>

.travis.yml

@@ -1,19 +1,22 @@
 dist: bionic
 language: go
 go:
-  - 1.11.x
   - 1.12.x
+  - 1.13.x
+  - 1.x
   - tip
 
 matrix:
   include:
     - go: 1.12.x
+      name: "cgroup-systemd"
       env:
         - RUNC_USE_SYSTEMD=1
       script:
         - make BUILDTAGS="${BUILDTAGS}" all
         - sudo PATH="$PATH" make localintegration RUNC_USE_SYSTEMD=1
     - go: 1.12.x
+      name: "cgroup-v2"
       env:
         - VIRTUALBOX_VERSION=6.0
         - VAGRANT_VERSION=2.2.6
@@ -29,6 +32,7 @@ matrix:
         - ssh default sudo podman run --privileged --cgroupns=private test make localunittest
   allow_failures:
     - go: tip
+    - name: "cgroup-v2"
 
 go_import_path: github.com/opencontainers/runc