Make "/butler" URL prefix variable in client

For phalanx deployments, all butler servers will have the same hostname but live under different paths.

python/lsst/daf/butler/remote_butler/_remote_butler.py

@@ -326,8 +326,7 @@ def _get_url(self, path: str, version: str = "v1") -> str:
         Parameters
         ----------
         path : `str`
-            The relative path to the server endpoint. Should not include the
-            "/butler" prefix.
+            The relative path to the server endpoint
         version : `str`, optional
             Version string to prepend to path. Defaults to "v1".
 
@@ -336,5 +335,4 @@ def _get_url(self, path: str, version: str = "v1") -> str:
         path : `str`
             The full path to the endpoint
         """
-        prefix = "butler"
-        return f"{prefix}/{version}/{path}"
+        return f"{version}/{path}"

tests/test_server.py

@@ -78,6 +78,7 @@ def create_factory_dependency():
 
         # Set up the RemoteButler that will connect to the server
         cls.client = TestClient(app)
+        cls.client.base_url = "http://text.example/butler/"
         cls.butler = _make_remote_butler(cls.client)
 
     @classmethod