Certain SCSI drivers do not allow certain tuning parameters
like nr_requests, max_sectors_kb to be changed, ignore these
errors silently as this script is simply a best effort.
Fixes#6103
- removes backend/{fs,xl} files.
- removes FreeBSD doc since we already have FreeNAS doc.
- removes sets/ directory which is redundant with
large-bucket directory.
- removes browser/ directory which attempts
to explain about browser RPC calls, since
its an internal API we do not need to document it.
Li Yi