oeqa/concurrencytest: Add number of failures to summary output

When running oe-selftest and seeing the end of a running log, it is
extremely helpful to know if there have been failures or not to save
looking at the rest of the log. Add the number of failures to the summary
line so that people monitoring builds have an easier time before the end
totals are printed.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>