Fix web-server memory overrun when downloading objects from Swift

[OpenStack Infra]

https://review.openstack.org/161204
commit 46405d456d9b056e648a4e60235b4c1b251f1236
Author: Timur Sufiev <email address hidden>
Date: Wed Mar 4 16:15:04 2015 +0300

    Fix web-server memory overrun when downloading objects from Swift

    To prevent memory overrun when downloading large objects from Swift
    * `resp_chunk_size` keyword should be passed to swiftclient
    * `obj.data` iterator returned from swiftclient is passed to HttpResponse
      (or StreamingHttpResponse for Django>=1.5) as usual since both response
      classes work with iterators/files/byte strings (yet StreamingHttpResponse
      does it better).

    The commit introduces new setting SWIFT_FILE_TRANSFER_CHUNK_SIZE that
    defines the size of chunk in bytes for Swift objects downloading.

    DocImpact

    Change-Id: I18e5809b86bfa24948dc642da2a55dffaa1a4ce1
    Closes-Bug: #1427819

[Lana (loquacity)]

This should be added to dev docs.

[Alexandra Settle (alexandra-settle)]

If this should be added to the dev docs, throwing back over the fence to horizon :)

Thanks team.

[Gary W. Smith (gary-w-smith)]

Closing, since the dev doc change was part of the horizon change.