More correct file_data handling in populators.py.

Any of file_N|file_data fields can have attached data.

test/base/populators.py

@@ -276,9 +276,14 @@ def get_remote_files(self, target="ftp"):
         return self._get("remote_files", data={"target": target}).json()
 
     def run_tool_payload(self, tool_id, inputs, history_id, **kwds):
-        if "files_0|file_data" in inputs:
-            kwds["__files"] = {"files_0|file_data": inputs["files_0|file_data"]}
-            del inputs["files_0|file_data"]
+        # Remove files_%d|file_data parameters from inputs dict and attach
+        # as __files dictionary.
+        for key, value in list(inputs.items()):
+            if key.startswith("files_") and key.endswith("|file_data"):
+                if "__files" not in kwds:
+                    kwds["__files"] = {}
+                kwds["__files"][key] = value
+                del inputs[key]
 
         return dict(
             tool_id=tool_id,