ionice rootwrap config doesn't cover every option pattern

[Tomoki Sekiyama]

Cinder may execute dd with iflag=direct OR oflag=direct (or both) options under ionice.
https://github.com/openstack/cinder/blob/master/cinder/volume/utils.py#L183

However, currently rootwrap only covers ionice+dd with both iflag AND oflag options.
https://github.com/openstack/cinder/blob/master/etc/cinder/rootwrap.d/volume.filters#L46

Since ChainingRegExpFilter is merged to oslo.rootwrap, now we can use this to allow ionice to be combined with the other allowed commands including 'dd'.
https://github.com/openstack/oslo.rootwrap/blob/master/README.rst#chainingregexpfilter

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/102667

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/102667
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=bb1579090b56b4de33bb3873b34ca6601f95dd56
Submitter: Jenkins
Branch: master

commit bb1579090b56b4de33bb3873b34ca6601f95dd56
Author: Tomoki Sekiyama <email address hidden>
Date: Wed Jun 25 16:50:18 2014 -0400

    Rewrite ionice command filter using ChainingRegExpFilter

    Currently, the ionice command prepended to a dd command is allowed by three
    rootwrap RegExpFilter's that cover 3 arguments patterns. However, this
    doesn't support if either 'iflag=direct' or 'oflag=direct' is omitted.
    Because of this problem, deletion of volumes may fail if volume_clear_ionice
    is set, as 'iflag=direct' is omitted.

    This commit fixes this problem by replacing the filters with
    ChainingRegExpFilter's, which allow to execute ionice to be combined with the
    other allowed commands, including 'dd'.

    Originally '-c[0-3]( -n[0-7])?' was allowed as an ionice option, but it is
    invalid to specify -n[0-7] in a single option (for example, when '-c2 -n7'
    is specified, ionice causes an error "invalid class argument: '2 -n7'").
    In this patch, 2 filters are provided to cover the case only with -c option
    and the case with both -c and -n options.

    Change-Id: Ia074bf3244b7f010bd9e3b5e46c3152c1848f3d3
    Signed-off-by: Tomoki Sekiyama <email address hidden>
    Closes-Bug: 1334422