do not test apt proxy if not running campusmanager

tests/test_apt_proxy.py

@@ -14,6 +14,10 @@ GREEN = '\033[92m'
 RED = '\033[91m'
 DEF = '\033[0m'
 
+if not os.path.exists('/etc/nginx/sites-enabled/skyreach.conf'):
+    print('Server not running CampusManager, skipping test')
+    sys.exit(0)
+
 os.chdir(os.path.dirname(__file__))
 if not os.path.isfile('../utils.py'):
     print('conf.sh not found')