vlan: fix many_vlans cleanup
Do not rely on NM deleting interface after connection delete, it might take some time, delete it sooner if 20s is not enough. Wait until NM syncs devices and next start command will not timeout.
@os:Fedora-Rawhide
@os:Fedora-40
@os:rhel8.10
@os:rhel9.5
@os:rhel10.0