Foreman Maintain

Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1721378

Description of problem:

foreman-maintain backup offline failed with undefined method `&' for "":String

- All services stopped [OK]
--------------------------------------------------------------------------------
Backup config files:
\ Collecting config files to backup [FAIL]
undefined method `&' for "":String
--------------------------------------------------------------------------------
Scenario [Backup] failed.

The following steps ended up in failing state:

[backup-config-files]

Resolve the failed steps and rerun
the command. In case the failures are false positives,
use --whitelist="backup-config-files"

Version-Release number of selected component (if applicable):

Satellite 6.6 snap 7

1. rpm -qa | grep maintain
   satellite-maintain-0.0.1-1.el7sat.noarch
   rubygem-foreman_maintain-0.4.3-1.el7sat.noarch

How reproducible: always

Steps to Reproduce:
1. # foreman-maintain backup offline -y --features dns,tftp,dhcp,openscap /tmp/

Actual results:
foreman-maintain backup offline failed.

Expected results:
Successful backup.

Additional info: Regression.