Reporting: In history tables, show multiple failure steps

Reporting: In history tables, show multiple failure steps

In report_run_getinfo, used by sg-report-job-history and
sg-report-host-history, make provision for reporting multiple failed
steps.

The failed steps are put side by side (in a single table cell).  The
cell background is set by the job status, but the individual steps may
vary their colour, as seen in this example:
  http://xenbits.xen.org/people/iwj/2015/linux-next.html

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
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v2: Remove unnecessary space in ColourAttr