xenapi: fixup bittorrent plugin for better performance and less logging

[Christopher Lefelhocz]

The bittorent plugin currently has some settings which could use some improvement. We have this data and would like to get
it upstream.
Specific issues covered:
- Increase the amount of disk queued bytes by double to improve downloading (we can queue more and not stall downloads)
- Allow download/uploads to run non-uniform since we are not a DSL Line.
- Also the plugin logs ever second and that is somewhat excessive. Would like to log only every 10 seconds.

[John Garbutt (johngarbutt)]

Leif, could you please give some more context on this one please? Not sure what you are trying to change here.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/85427
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=5255364933e0255f6af2a895a90ee62a62abc07e
Submitter: Jenkins
Branch: master

commit 5255364933e0255f6af2a895a90ee62a62abc07e
Author: Christopher Lefelhocz <email address hidden>
Date: Wed Apr 2 06:32:11 2014 -0500

    XenAPI: adjust bittorrent settings

    This commit addresses some optimizations when using libtorrent to
    download. The settings are documented here:
    http://www.rasterbar.com/products/libtorrent/reference-Settings.html

    I'm proposing to add these with dom0 environment overrides in case
    any other adjustments are needed. The changes effectively double the
    download rate from the default settings. It also allows unbalanced
    download/upload which is preferred in openstack environments.

    No unit tests were added as plugins are not currently unit tested.

    Closes-bug: #1303993

    Change-Id: I503a6a521c196e4ad58e0a16aba2988f66a9cdca