These filter tests need a NIC, no matter which one, so they use a common
NIC by default. However, these common NIC models might not always have
been compiled into the QEMU target binary, so assuming that a certain NIC
is available is a bad idea. Since the exact type of NIC does not really
matter for these tests, let's switch to "-nic" instead of "-netdev" so
that QEMU can simply pick a default NIC for us.
This way we can now run the tests on other targets that have a default
machine with an on-board/default NIC, too.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20211220103025.311759-1-thuth@redhat.com>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>