Update variable names after slave_of references removal

[Victoria Martinez de la Cruz]

In https://review.openstack.org/#/c/245845 the last vestiges of slave_of were removed for good. Still, the variable names and comments using this term were preserved. Having clear variable names helps people to understand what they are reading. It will be certainly misleading for new developers that missed this change to read "slave_of_id" and get a "replica_of" in the other side.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/309164

[OpenStack Infra (hudson-openstack)]

Change abandoned by Gage Hugo (<email address hidden>) on branch: master
Review: https://review.openstack.org/309164
Reason: reverted because it was a backward incompatible change and the stable jobs were failing

[Gage Hugo (gagehugo)]

According to mariam john:

This was reverted because it was a backward incompatible change and the stable jobs were failing because of this.

[Amrith Kumar (amrith)]

Are you still working on it?

[Gage Hugo (gagehugo)]

If changing just the variable names is ok, then yes I would like to fix this.

[Amrith Kumar (amrith)]

I believe that this is the subject of this bug. something else would fix the API and stuff, this was to fix the variable names in the code. Check with vkmc but I think this was the result of a set of code review discussions.