tests/acceptance/virtiofs_submounts: use workdir property

For Avocado Instrumented based tests, it's a better idea to just use
the property.  The environment variable is a fall back for tests not
written using that Python API.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Beraldo Leal <bleal@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reference: https://avocado-framework.readthedocs.io/en/84.0/api/test/avocado.html#avocado.Test.workdir


Message-Id: <20210203172357.1422425-5-crosa@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

tests/acceptance/virtiofs_submounts.py

@@ -136,8 +136,7 @@ def run(self, args, ignore_error=False):
         return (stdout, stderr, ret)
 
     def set_up_shared_dir(self):
-        atwd = os.getenv('AVOCADO_TEST_WORKDIR')
-        self.shared_dir = os.path.join(atwd, 'virtiofs-shared')
+        self.shared_dir = os.path.join(self.workdir, 'virtiofs-shared')
 
         os.mkdir(self.shared_dir)
 
@@ -234,8 +233,7 @@ def setUp(self):
 
         self.seed = self.params.get('seed')
 
-        atwd = os.getenv('AVOCADO_TEST_WORKDIR')
-        self.ssh_key = os.path.join(atwd, 'id_ed25519')
+        self.ssh_key = os.path.join(self.workdir, 'id_ed25519')
 
         self.run(('ssh-keygen', '-t', 'ed25519', '-f', self.ssh_key))