Extend known-issues.sh script (#136)
Extend known-issues.sh script (#136)

* Added "Pass" column which includes the number of times the
  test has passed in the given branch or pull request.

* Added "Rate" column which shows the observed failure rate;
  calculated as "Fail / (Pass + Fail)" and show as a percentage.

* The cutoff values for severity are now expressed as a rate;
  low (<= 1%), medium (<= 5%), high (> 5%)

* Added "Failure List" column with links to the builds for
  all failed tests.

Signed-off-by: Brian Behlendorf <32d50ad1e384dcb9a5bf7e40fa470df5dabaf348@llnl.gov>
gmelikov/zfs-buildbot,zfsonlinux/zfs-buildbot,gmelikov/zfs-buildbot,zfsonlinux/zfs-buildbot