tests: make before/after items an array in schema test (#2465)

The theory for why this doesn't always fail is because, as of
2a2f798, the schema is no longer an
ordered dict, which makes the order in which validation finds multiple
issues non-deterministic.

Signed-off-by: Kyle Fazzari <kyrofa@ubuntu.com>

tests/unit/project/test_schema.py

@@ -163,8 +163,8 @@ class DaemonDependencyTest(ValidationBaseTest):
             "post-stop-command",
             dict(option="post-stop-command", value="binary1 --post-stop"),
         ),
-        ("before", dict(option="before", value="service2")),
-        ("after", dict(option="after", value="service2")),
+        ("before", dict(option="before", value=["service2"])),
+        ("after", dict(option="after", value=["service2"])),
     ]
 
     def test_daemon_dependency(self):