MFC r237689 (by imp):

MFC r237689 (by imp):
Add a sysctl to set the cdrom timeout.  Data recovery operations from
a CD or DVD drive with a damaged disc often benefit from a shorter
timeout.  Also, when retries are set to 0, an application is expecting
errors and recovering them so do not print the error into the log.
The number of expected errors can literally be in the hundreds of
thousands which significantly slows data recovery.

git-svn-id: svn://svn.freebsd.org/base/stable/9@249135 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f