ci: Rename Arch container to make it clear we're testing on rolling base

.travis.yml

@@ -46,9 +46,9 @@ matrix:
       os: linux
       env: CONTAINER=opensuse1500
       services: docker
-    - name: "Archlinux 2018.01.01"
+    - name: "Archlinux Base (Rolling)"
       os: linux
-      env: CONTAINER=arch180101
+      env: CONTAINER=arch
       services: docker
     - name: "Mac OS X 10.13"
       os: osx

docker-compose.yml

@@ -88,10 +88,10 @@ services:
     security_opt:
       - label=type:container_runtime_t
     tty: true
-  test-arch180101:
+  test-arch:
     build:
         context: .
-        dockerfile: test/docker/arch180101
+        dockerfile: test/docker/arch
     network_mode: "host"
     security_opt:
       - label=type:container_runtime_t