Use df(1) in a portable way

The _get_capacity_info() method of glance.store.filesystem.Store
class calls df(1) with '--block-size' GNU-speicifc argument
to get 1 byte blocks.

To make this code more portable [1], call df(1) with '-k' argument to
get 1024 byte blocks and multiply the result by 1024.

1: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/df.html

Change-Id: I7ab2eb1c8588fec3623046ddc91615ba2eba2c13
Assign local variable in api.v2.image_data

If local variable 'image' will be not initialized we get UnboundLocalError
while handle following exceptions:
exception.StorageFull
exception.StorageQuotaFull
exception.ImageSizeLimitExceeded
exception.StorageWriteDenied
webob.exc.HTTPError
ValueError

This is because not initialized variable 'image' used as argument of
method _restore. That is why we should initialize it.

Closes-Bug: #1310952

Change-Id: I3bf73ca272aad479416067495006476934a01dd9
colorizer: use staticmethod rather than classmethod

The methods are actually not class methods at all as they do not use the
class nor the instance.

Change-Id: I04721bcaef30da291389a1144bdcfe65f10753b2
notifier: remove notifier_strategy compat support

The notifier_strategy option is deprecated since we merged commit
I8cd84772bc5867e06b2a50ed7e15b9e86f0b94ad during the Icehouse cycle.

Assuming the usual single cycle deprecation period, this can now be
removed.

DocImpact: the notifier_strategy has been removed in favor of the
notification_driver and related oslo.messaging options.

Change-Id: I3ab0133b697a820536e5da84e30b078915a29f6c
Add pluging sample for glance gate

Recently we add support for plugins in gates, so now you are able
to keep rally benchmarks in your source tree. It may be usefull in cases
when you would like to check/debug in gates with benchmark that doens't exist
in Rally but don't want to spend whole life to get in Rally source.

As well we add extra/ directory that is just copy pasted in gates.
So we can use absolute path in task configs, cause this directory
will be copy pasted to ~/.rally/extra. This may be super usefull if you
would like to test infrastracture on scale, creating images from empty files.

Change-Id: I759ee8bf7a930169afd6076ec96f8fe3a3692866
Changed psutil dep. to match global requirements

Global requirements now expect that psutil<2.0.0
Therefore the call to children() in psutil was
invalid and was failing tests, so this commit
changes the call to get_children() and updates
test-requirements to reflect this version change

Change-Id: I9570dd1ec0cb9fd7efaee292d7996510b56ab611
Merge "Changed psutil dep. to match global requirements"
Updated from global requirements

Change-Id: Id99428645bdc0406071e149b92ea2541587617c2
Merge "Use df(1) in a portable way"
Merge "colorizer: use staticmethod rather than classmethod"
Merge "notifier: remove notifier_strategy compat support"
Merge "Assign local variable in api.v2.image_data"
Merge "Updated from global requirements"
Merge "Add pluging sample for glance gate"