cats: include only jobtypes in list jobtotals that write data to volumes

[fbergkemper]

The list jobtotals command should only summarize jobs
that have actually written to a storage.

These are the jobtypes B, A, a and C. Other jobtypes
like O and R should be excluded from jobtotals.

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[pstorz]

The title says that certain job types are excluded, but in fact only certain job types are included if I look at the code. The suggested title is in the CHANGELOG.md change suggestion.

[pstorz]

Good work!