Enhance logging_UserCrash to detect problems with crash reporting setup

This is to help catch problems like the recent one where the
core pattern sysctl wasn't being set up correctly.  logging_UserCrash
would override the pattern for it's testing and wouldn't see that
no crash reports would actually get generated.

BUG=chromium-os:12627
TEST=run logging_UserCrash with a known good core pattern and a known bad pattern

Change-Id: I15d1fc11a77ef8eb586a4166f5da851a4cc65624

Review URL: http://codereview.chromium.org/6625038
1 file changed