crush: fix map->choose_tries boundary test

CrushWrapper::start_choose_profile allocates map->choose_tries with
choose_total_tries elements. When crush_choose_firstn sets a value, it
tests against map->choose_local_tries which could lead to memory
corruption if map->choose_total_tries is smaller than
map->choose_local_tries.

Another indesirable but non fatal side effect is that the output crushtool
--show-choose-tries will be truncated to choose_local_tries which is
set to a lower value than choose_total_tries by the default tuneables.

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #922 from dachary/wip-crush-choose-tries

crush: fix map->choose_tries boundary test

Reviewed-by: Sage Weil <sage@inktank.com>
Merge git://github.com/ceph/ceph