Adds tests covering Swift's Account Quota middleware

The execution of the tests is conditional to a setting declared
in the config file.

There are 2 tests:
 + User uploads an object smaller than the quota successfully
 + User fails to upload an object larger than the quota

Note that this test assumes that the admin account has the
ResellerAdmin role.

Change-Id: I00dd1b88d4d9b65b4c6f5b9cc6b1c8704bdc9d8b
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 825965f..6cc7179 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -259,6 +259,8 @@
 # Number of seconds to wait while looping to check the status of a
 # container to container synchronization
 container_sync_interval = 5
+# Set to True if the Account Quota middleware is enabled
+accounts_quotas_available = True
 
 [boto]
 # This section contains configuration options used when executing tests