4598: formatting and calculation fixes (code review)

4598: formatting and calculation fixes (code review)

Incorporating code review feedback from #4598-13.

Bugs fixed:
* Correct counting and percentage calculation of job failures.
** Jobs were getting categorized as both "unknown" and as a specific failure type.
* Crashes fixed: should not raise any unhandled exceptions.

Formatting fixes:
* Itemized failures are now sorted in descending order by failure type
* Better horizontal alignment
* Modified formatting to account for updated description.