Merge pull request #955 from ceph/wip-crush-2

crush: make set_chooseleaf_tries work with firstn chooseleaf, too

Reviewed-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: Loic Dachary <loic@dachary.com>

diff --cc qa/workunits/cephtool/test.sh
Simple merge

diff --cc src/common/config_opts.h
Simple merge