Removing keystone account creation

Reasons:
- Currently devstack creates the users 'admin', 'demo', and
  'alt_demo' so there is no need to create any extra users
  for the integration tests.

Changes:
- Removing custom keystone user creation from redstack.
- Replacing users in test_begin.conf with devstack ones.
- Changed glance, swift, and rd commands to use the openrc
  helper script to log in as 'admin' or 'demo'
- Changed the report_directory sed line to match the others
  in the mod_test_conf function.

Closes-Bug: #1265829

Change-Id: I59dd1e94aa40d87d8b69009fbfa2a7205ea822d0
Merge "Removing keystone account creation"