security service fields can not be unset after set operation

[Valeriy Ponomaryov]

It is impossible to unset some value from security service if it was set.

See related code: https://github.com/openstack/python-manilaclient/blob/620b54ec/manilaclient/v1/security_services.py#L96

It should be possible to revert back some changes to security services as well as for shares and snapshots.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/214577

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/214577
Committed: https://git.openstack.org/cgit/openstack/python-manilaclient/commit/?id=4fcccf9e386a5b83790a82d76d74903f9f7db13c
Submitter: Jenkins
Branch: master

commit 4fcccf9e386a5b83790a82d76d74903f9f7db13c
Author: Julia Varlamova <email address hidden>
Date: Wed Aug 19 07:55:55 2015 -0400

    Allow user to unset security service params

    It is impossible to unset some value from security service if it was set.
    Allow user to set security service params (dns_ip, server, domain,
    user, password, name, description) to empty value.

    Closes-bug: #1446696

    Change-Id: Ifea8f49b2007358565686f90a5d56476c4913c86