[tests] don't flush closed log files

Change-Id: Ia5fe1ab6f386a9e754a9262809927fbbe22b30c7

Author: stbuehler

tests/pylt/logfile.py

@@ -31,7 +31,8 @@ def close(self) -> None:
             super().close()
             self._file.close()
             for f in self._clones.values():
-                f.flush()
+                if not f.closed:
+                    f.flush()
 
     def writable(self) -> bool:
         return True
@@ -63,9 +64,11 @@ def write(self, /, data: str) -> int:
         return len(data)
 
     def flush(self) -> None:
-        self._file.flush()
-        for f in self._clones.values():
-            f.flush()
+        if not self.closed:
+            self._file.flush()
+            for f in self._clones.values():
+                if not f.closed:
+                    f.flush()
 
 
 class RemoveEscapeSeq(io.TextIOBase):