Comment 4 for bug 1846836

Reviewed: https://review.opendev.org/688543
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=0c10d54a096de7dbdf6eb1d781753317325f64db
Submitter: Zuul
Branch: stable/train

commit 0c10d54a096de7dbdf6eb1d781753317325f64db
Author: silvacarloss <email address hidden>
Date: Wed Oct 9 14:25:57 2019 +0000

    Fix share network update erroneously returns success

    This patch fixes an issue while performing share network update.
    Manila was allowing the user to update a share network even if it
    did not contain a default subnet. Now, we throw an error if there
    is no default subnet to be updated. Also, adds an extra validation.
    Now, Manila do not allow the default share network subnet update if
    it is going to have only `neutron_net_id` or `neutron_subnet_id`
    after the update.

    Change-Id: Iba2761db53da68a1c497e2e5dd370c36a22ebbed
    Closes-Bug: #1846836
    (cherry picked from commit de2d94172bebc8d8771e2e67860d94559a86cece)