tests/functional: Add missing require_netdev('user') statements

A bunch of tests are using "-netdev user" but fail to check
for the availability of SLIRP in the binary, so these tests
fail if QEMU has been configured with "--disable-slirp"
(most of the tests are disabled by default with a decorator,
that's likely why nobody noticed this problem yet). Add the
missing self.require_netdev('user') statements to skip the
tests if SLIRP is not available.

Message-ID: <20250324123450.111307-1-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/functional/test_aarch64_rme_virt.py

@@ -60,8 +60,10 @@ class Aarch64RMEVirtMachine(QemuSystemTest):
     # and launching a nested VM using it.
     def test_aarch64_rme_virt(self):
         self.set_machine('virt')
-        self.vm.set_console()
         self.require_accelerator('tcg')
+        self.require_netdev('user')
+
+        self.vm.set_console()
 
         stack_path_tar_gz = self.ASSET_RME_STACK_VIRT.fetch()
         self.archive_extract(stack_path_tar_gz, format="tar")