Description of problem:

If the firewall rules are flushed by the user then custom chain set by foreman-maintain (FOREMAN_MAINTAIN) will be deleted and upgrade through foreman-maintain fails since we could not turn off maintenance mode successfully.

Running Procedures after migrating to Satellite 6.2.z
================================================================================
katello-service start: 
/ No katello service to start                                         [OK]      
--------------------------------------------------------------------------------
Turn off maintenance mode:                                            [FAIL]
Failed executing iptables -D INPUT -j FOREMAN_MAINTAIN, exit status 1:
 iptables: No chain/target/match by that name.
--------------------------------------------------------------------------------
Scenario [Procedures after migrating to Satellite 6.2.z] failed.

The following steps ended up in failing state:

  [maintenance-mode-disable]


Additional Info: 
This bz is created with the reference of: https://bugzilla.redhat.com/show_bug.cgi?id=1524279#c3 to track different issues in different bz.