qa/workunit:  Add dbench-short.sh for nfs suite

    A multi-client dbench run doesn't work over NFS,
    see bug #3718.  Make single client dbench available.

    Signed-off-by: David Zafman <david.zafman@inktank.com>
doc: Fixed syntax error.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added some packages to the copyable line.

Fixes: #3686

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added comments on --without-tcmalloc option when building Ceph.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added defaults for PGs, links to recommended settings, and updated note on splitting.

Fixes: #3555

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
Merge git://github.com/ceph/ceph