Add option to choose partition alignment mode

[OpenStack Infra]

https://review.openstack.org/330112
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commit d2185b1316cf72e1e899eb309e4bffcdd7ff8a0e
Author: Alexander Gordeev <email address hidden>
Date: Thu May 5 15:52:40 2016 +0300

    Add option to choose partition alignment mode

    Under certain circumstances due to that alignment, the end of
    particular partition could cross 1M boundary. And due to actual
    partition' bounderies being rounded up, fuel-agent mistakenly
    assumes that partition couldn't fit within provided boundaries
    and raises errors.WrongPartitionSchemeError.

    However, some h/w data storages are well known for reporting
    relatively huge optimal IO sizes (16M or even bigger), so the 1M
    room can't be enough. Thus, optimal aligning is not an option.
    In such cases, it's better to proceed with minimal mode.

    It's the minimum aligment needed to align the partition properly
    to physical blocks which avoids performance degradation.

    Partial-Bug: #1543233
    DocImpact

    Conflicts:

     bareon/drivers/deploy/nailgun.py
     fuel_agent/tests/test_manager.py

    Change-Id: I1dd94731f497f3deb47cec9a23957e3706c2fb3b