chunker_test: fix import issue

name collision: module buzhash vs function buzhash.

src/borg/chunkers/__init__.py

@@ -1,6 +1,6 @@
-from .buzhash import *  # noqa
-from .failing import *  # noqa
-from .fixed import *  # noqa
+from .buzhash import Chunker
+from .failing import ChunkerFailing
+from .fixed import ChunkerFixed
 from .reader import *  # noqa
 
 API_VERSION = "1.2_01"

src/borg/testsuite/chunker_test.py

@@ -3,7 +3,9 @@
 
 from io import BytesIO
 
-from ..chunkers import ChunkerFixed, Chunker, get_chunker, buzhash, buzhash_update
+from ..chunkers import get_chunker
+from ..chunkers.fixed import ChunkerFixed
+from ..chunkers.buzhash import buzhash, buzhash_update, Chunker
 from ..constants import *  # NOQA
 from . import BaseTestCase