New commit detected on ManageIQ/manageiq/gaprindashvili:

https://github.com/ManageIQ/manageiq/commit/54ec113077d242bb804770698601291a040deb80
commit 54ec113077d242bb804770698601291a040deb80
Author:     Gregg Tanzillo <gtanzill@redhat.com>
AuthorDate: Wed Jul 18 16:46:18 2018 -0400
Commit:     Gregg Tanzillo <gtanzill@redhat.com>
CommitDate: Wed Jul 18 16:46:18 2018 -0400

    Merge pull request #17692 from juliancheal/filter_by_flavor_api

    Adding flavor as a has one on VM
    (cherry picked from commit fb7a26da221d315639bf6851d646522db54f5d17)

    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1607441

 app/models/vm_or_template.rb | 1 +
 1 file changed, 1 insertion(+)

Verified on 5.9.4.2 that it's possible to filter by flavor name:

GET /api/vms?filter[]=flavor.name=m3.medium
{
    "name": "vms",
    "count": 38,
    "subcount": 1,
    "subquery_count": 1,
    "pages": 1,
    "resources": [
        {
            "href": "https://<addr>/api/vms/792"
        }
    ],
...

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2018:2561