Make RequestContext use auth_token (not auth_tok)

The RequestContext class from oslo-incubator uses 'auth_token'.
Glance's RequestContext uses 'auth_tok' -- which is inconsistent.

glance_store currently uses the oslo 'auth_token'.

We should not assume a 1-1 mapping from the glance_store to glance,
nor should we have glance_store support both 'auth_token' and
'auth_tok'. Therefore Glance should be updated to use 'auth_token'.

This change was generated automatically with:

$ for file in `find glance -name '*\.py' -exec grep -wl auth_tok "{}" \;` ; \
  do sed --in-place 's/\<auth_tok\>/auth_token/g' $file ; done

In addition, the set_auth_token function was removed. This had been used
by Nova to work around the auth_tok <-> auth_token inconsistency, but
was removed in mid-2012 as part of the move to python-glanceclient so
is no longer needed.

In conjuction with other changes this fixes image upload when
using the multi-tenant Swift store.

Change-Id: Ic8a5f44088990fd8f6290a5622b823f59ef365fc
Partial-bug: #1385213
(cherry picked from commit cc7ae2abd5c67b5573ca609e27c79d5c4f9a528d)
Merge "Make RequestContext use auth_token (not auth_tok)" into stable/juno