known-issues.sh: updated log file name
known-issues.sh: updated log file name

After some recent changes the name of the ZTS log file has
changed resulting in no failed testing being found.  Update
the expected log file name to correct this.

Signed-off-by: Brian Behlendorf <32d50ad1e384dcb9a5bf7e40fa470df5dabaf348@llnl.gov>

zfsonlinux/zfs-buildbot,zfsonlinux/zfs-buildbot