burnin: Ignore item order when checking quotas equality

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Adjust pithos tests to Synnefo v0.16

Make sure to validate quotas after every action that affects them.

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Check pithos API for unicode header key handling