Move auth config from api-paste.ini to nova.conf.

In Icehouse, the configurations for keystone auth token has been moved
to nova.conf. So we need to remove the configurations from api-paste.ini
and move them to nova.conf.

Change-Id: I5b5b32b16c8e9235103bd61f3c3eb1774b093e0a
Closes-Bug: #1342002