Member role preservation logic not working on newton->ocata upgrade

There are a couple of problems here:

1) The logic for checking if stackrc exists during the undercloud install is broken, which means this method always reports that the member role does not exist. See https://review.openstack.org/#/c/432435/

2) Even with the fix referenced above, the undercloud upgrade job is still failing with a connection error to keystone.* Considering the current broken logic, I suspect this code was never actually run before and likely never worked.

This is fairly serious as it could break the undercloud heat configuration on upgrade, at least if I understand the original motivation for the code correctly.

* http://logs.openstack.org/35/432435/1/check/gate-tripleo-ci-centos-7-undercloud-upgrades-nv/62bd182/