torture: Abbreviate console error dump

Currently, the scripts print a list of warning/bug indicators from the
console.log file.  This works well if there are only a few warnings or
bugs, but can be quite annoying if there is a large number.  This commit
therefore prints a summary listing the number of each type of warning/bug
indicator, but only if there is at least one such indicator.  The full
list is stored in the results directory at console.log.diags, which
makes it easier to find the warning/bugs in the full console.log.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>