Merge pull request #629 from netbootxyz/centos_7.8

Bump for CentOS 7.8

roles/netbootxyz/defaults/main.yml

@@ -127,8 +127,8 @@ releases:
       name: '8.0'
     - code_name: 8-stream
       name: 8.0 Stream
-    - code_name: 7.7.1908
-      name: '7.7'
+    - code_name: 7.8.2003
+      name: '7.8'
   coreos:
     base_dir: prod/streams/stable/builds
     enabled: true