Comment 2 for bug 1809647

Reviewed: https://review.openstack.org/627169
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=785435a18f65fe85561d3ad39a2dfaf19b44bb41
Submitter: Zuul
Branch: master

commit 785435a18f65fe85561d3ad39a2dfaf19b44bb41
Author: Yikun Jiang <email address hidden>
Date: Mon Dec 24 17:41:04 2018 +0800

    Fix CI failed: test_get_volume_filter_options_using_config

    Recently, CI failed(py27, py35 and other unit tests) due to
    test_get_volume_filter_options_using_config case.

    In patch[1], we remove deprecated query_volume_filters config option,
    but the test case is fixed by a wrong way. The
    ``CONF.resource_query_filters_file`` is a **json path**, but NOT a
    **json str**, if we want to overwrite it, we should overwrite the
    _FILTERS_COLLECTION.[2]

    Unfortunately, if we have already called the _initialize_filters in
    other case (before this case), this error will not be exposed. So, we
    didn't find this error occurring in first-CI.

    This patch try to fix this issue.

    Co-Authored-By: wanghao <email address hidden>

    Closes-bug: #1809647

    [1] https://review.openstack.org/#/c/620632/
    [2] https://review.openstack.org/#/c/620632/2/cinder/api/common.py@356

    Change-Id: I190cc67a001ffce2a533480e6e39e26cd3f981df