Change keystone.log's permit to keystone:keystone

At present, keystone.log's user:group permit is root:kolla,
when got token from keystone, it failed. The reason is that:
Permission denied. So it shoud be changed keystone:keystone.

Change-Id: Ibbbf1d88ba16e5040f9068ea9948373d10593514
Closes-Bug: #1631685