Avoid shadowing vars() built-in func in modules.openbsdservice._get_rc()

************* Module salt.modules.openbsdservice
salt/modules/openbsdservice.py:144: [W0622(redefined-builtin), _get_rc] Redefining built-in 'vars'
Merge pull request #11686 from hulu/vars-shadowing

Avoid shadowing vars() built-in func in modules.openbsdservice._get_rc()