tests/acceptance/virtiofs_submounts.py: add missing accel tag

The tag is useful to select tests that depend/use a particular
feature.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20210412044644.55083-2-crosa@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>

tests/acceptance/virtiofs_submounts.py

@@ -70,6 +70,7 @@ def test_something_that_needs_cmd1_and_cmd2(self):
 class VirtiofsSubmountsTest(LinuxTest):
     """
     :avocado: tags=arch:x86_64
+    :avocado: tags=accel:kvm
     """
 
     def get_portfwd(self):