Fix pipeline premoderation/unit-tests

Do not run unit-tests for master merges.
Fix the permissive "null" user.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

.gitlab-ci.yml

@@ -415,7 +415,7 @@ syntax-check:
   script:
     - ansible-playbook -i inventory/local-tests.cfg -u root -e ansible_ssh_user=root  -b --become-user=root cluster.yml -vvv  --syntax-check
     - /bin/sh scripts/premoderator.sh
-  except: ['triggers']
+  except: ['triggers', 'master']
 
 tox-inventory-builder:
   stage: unit-tests
@@ -424,4 +424,4 @@ tox-inventory-builder:
     - pip install tox
     - cd contrib/inventory_builder && tox
   when: manual
-  except: ['triggers']
+  except: ['triggers', 'master']