Invert boolen logic for a check in auth backend

This should repair the issue @ #4281
Merge pull request #4343 from sfdc-kho/develop

Add workaround for https://github.com/saltstack/salt-api/issues/61
Revert "Add workaround for https://github.com/saltstack/salt-api/issues/61"

This reverts commit a42ccf1b0142ca062ce3ffdf5ad9b0a4257e1dbc.