Rename "endpoint" to "credentials" over the code

[Boris Pavlovic]

We are using word "endpoint" for endpoints and for whole actually credentials. This should be fixed.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/242411

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/244405

[OpenStack Infra (hudson-openstack)]

Change abandoned by Bo Chi (<email address hidden>) on branch: master
Review: https://review.openstack.org/244405
Reason: duplicate to https://review.openstack.org/#/c/242411/

[Bo Chi (bochi-michael)]

After some attempts I think I will split this bug into 3 patches:

1. modify class name and file name from "Endpoint" to "Credential" and modify each place that uses objects.Endpoint
   mark objects.Endpoint as deprecated.
   key name in context objects is not changed in this patch
2. change key name in context objects from "endpoint" to "credential".
  Mark "endpoint" as deprecated after https://review.openstack.org/#/c/245094 is merged.
3. modify other variable names that need to be changed

Please let me know if my plan can be improved, thanks.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/242411
Committed: https://git.openstack.org/cgit/openstack/rally/commit/?id=ee73295e93be188b5f12d5b838b6bc9962122ba2
Submitter: Jenkins
Branch: master

commit ee73295e93be188b5f12d5b838b6bc9962122ba2
Author: Bo Chi <email address hidden>
Date: Sun Nov 15 04:21:26 2015 -0500

    Rename "endpoint" to "credential" (part 1)

    Copied rally/common/objects/endpoint.py to credential.py
    Marked objects.Endpoint as deprecated
    Modified use of objects.Endpoint to objects.Credential
    Variable and key names are not changed in this patch

    Partial-Bug: #1447682
    Change-Id: Ia62881473d1bf63f952528b66e7420eea6323f08

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/253442

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/253442
Committed: https://git.openstack.org/cgit/openstack/rally/commit/?id=f9145fd9eb1ad7ed330b1d0bc659862ccdf56c3c
Submitter: Jenkins
Branch: master

commit f9145fd9eb1ad7ed330b1d0bc659862ccdf56c3c
Author: Bo Chi <email address hidden>
Date: Fri Dec 4 05:43:32 2015 -0500

    Rename "endpoint" to "credential" (part 4)

    Changed key name in context and related strings to credential

    Change-Id: I41fafdd71584296037c5abb793e54e3055c033b5
    Closes-Bug: #1447682