Mesure request only return empty list if the timeframe is too small for the granularity

[Stéphane Albert]

Requesting measures from gnocchi doesn't return enough information if your start and stop timeframe is smaller than granularity.
Due to this we don't know if we get an empty response because there is no data or just because granularity is too high and gnocchi can't find a correct match.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/252525

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/252525
Committed: https://git.openstack.org/cgit/openstack/gnocchi/commit/?id=1b3025bf1c28c1faf7af94b7aaba2a1daf285e99
Submitter: Jenkins
Branch: master

commit 1b3025bf1c28c1faf7af94b7aaba2a1daf285e99
Author: Julien Danjou <email address hidden>
Date: Wed Dec 2 18:10:39 2015 +0100

    storage: round back from_timestamp in get_measures()

    This makes sure that if a user request "2014-01-01 12:23" and we have
    ("2014-01-01 12:20", 300), we do return this too.

    This avoids getting 0 point in the API request when the granularity is
    larger than the timespan requested.

    Change-Id: Id7c97308043419555514287df83c3f7cd96cca26
    Closes-Bug: #1520322