Upgrade to Red Hat Satellite 6 is failing because of invalid configuration in .hammer/defaults.yml

Issue

• Upgrade to Red Hat Satellite 6.4 fails when .hammer/defaults.yml exists

  Running preparation steps required to run the next scenarios
  ================================================================================
  Setup hammer:
  Configuring Hammer CLI...
  Hammer admin password:
                                                                        [FAIL]
  Hammer configuration failed: Is the admin password correct? (it was stored in /etc/foreman-maintain/foreman-maintain-hammer.yml)Is the server down?
  --------------------------------------------------------------------------------
  Scenario [preparation steps required to run the next scenarios] failed.
  The following steps ended up in failing state:
  [hammer-setup]
  Resolve the failed steps and rerun the command. In case the failures are false positives, use --whitelist="hammer-setup"
  

• When we have specified values in .hammer/defaults.yml (via the hammer defaults command) foreman-maintain will fail to authenticate and error on most commands.

  # foreman-maintain  health check
  Running preparation steps required to run the next scenarios
  ================================================================================
  Setup hammer: 
  Configuring Hammer CLI...
  Hammer admin password: 
                                                                      [FAIL]
  Hammer configuration failed: Is the admin password correct? (it was stored in /etc/foreman-maintain/foreman-maintain-hammer.yml)Is the server down?
  
  this makes it look like the password is incorrect or the server is down, when in fact, there may be a setting in ~./.hammer/defauts.yml that is invalid or conflicting with foreman-maintain's usage of hammer.
  
  This results in failed upgrades with difficulty determining why:
  
  # satellite-installer --upgrade
  ...
  Upgrade Step: Running installer...
  Installing             Done                                               [100%] [...........................................................................]
  The full log is at /var/log/foreman-installer/satellite.log
  Upgrade Step: restart_services...
  Redirecting to 'foreman-maintain service'
  Running preparation steps required to run the next scenarios
  =============================================================================
  Setup hammer: Configuring Hammer CLI...
  Hammer admin password: 
  
  
                                                                      [FAIL]