Recently FQDNs were needed for traffic flow tests [1],
but it seems AZ tests are affected as well from this fix.
This change fixes API network agent listing
for 'OVN Controller Gateway agent' to match short hostnames to zones.
Short hostnames used since API may show a mix of short/full names.
[1] 926195: Use long names when getting router gateway | https://review.opendev.org/c/x/whitebox-neutron-tempest-plugin/+/926195
Change-Id: Iafeced62b4ebe50a20f976803fd8a0cdbfeb3330