Setup cockpit only on Ubuntu 18.04

1.Base/4.cockpit/0_setup.py

@@ -4,12 +4,9 @@ import os
 
 
 def setup(interactive=False):
-    if os.path.exists('/etc/lsb-release'):
-        with open('/etc/lsb-release', 'r') as fo:
-            content = fo.read()
-        if '16.04' in content:
-            utils.log('Skipping cockpit setup because OS is Ubuntu 16.04.')
-            return
+    if os.system('lsb_release -a | grep "18.04"') != 0:
+        utils.log('Skipping cockpit setup because OS is not Ubuntu 18.04.')
+        return
     cmds = [
         'apt install -y software-properties-common',
         'add-apt-repository universe',