When running a "chio return" operation using a physical source unit
rather than a voltag name, do not set the CESR_VOLTAGS flags in the
CHIOGSTATUS command requesting the current status. As voltags are an
optional feature that must be handled as "reserved" by media changers
not implementing the feature, always setting CESR_VOLTAGS resulted in
the command being aborted with an `Invalid field in CDB', and
consequently the "chio return" failed, for media changers that do not
support voltags.

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