Update misplaced params of _format_remote_index_files

[lsongx]

Misplaced params:
_format_remote_index_files(cu.list_objects(), cu.remote)

Description of changes:

A quick fix of a small bug in #576
_format_remote_index_files(cu.list_objects(), cu.remote)
should be
_format_remote_index_files(cu.remote, cu.list_objects())

Issue #, if available:

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[XiaohanZhangCMU]

lgtm