burnin: Test integrity of Astakos endpoints

Enhance burnin's 'astakos' test suite with authenticate/endpoint tests.

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Add pithos account_head/get tests

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Add tests for pithos account POST

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Allow tests without proper doc header

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Create container_head tests

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Destroy created containers at tearDown

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test pithos object_copy

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test pithos container POST/PUT

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test everything up to object GET

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test object PUT

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test object COPY, refine object PUT

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test object MOVE

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test object POST

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test object DELETE

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Test image register with a unicode name

Reviewed-by: Ilias Tsitsimpis <iliastsi@grnet.gr>
burnin: Fix a bug when uploading an image

Use 'burnin-images' container when uploading/registering an image.