Remove unused configuration variables

* from the config sample
* from the config.py
* from the config template

Change-Id: Ic4c57f8c20d3e4107adc3a64b234fe578c4d899c
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index ed3cf6c..020baa1 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -210,12 +210,8 @@
 [object-storage]
 # This section contains configuration options used when executing tests
 # against the OpenStack Object Storage API.
-# This should be the username of a user WITHOUT administrative privileges
-username = admin
-# The above non-administrative user's password
-password = password
-# The above non-administrative user's tenant name
-tenant_name = admin
+
+# You can configure the credentials in the compute section
 
 # The type of endpoint for an Object Storage API service. Unless you have a
 # custom Keystone service catalog implementation, you probably want to leave