crush: output --show-bad-mappings on err

Instead of using stdout so that it displays well when used in
conjunction with --show-statistics

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: add CrushTester accessors

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: --show-utilization* implies --show-statistics

--show-utilization* outputs only if --show-statistics is set, which is
confusing. Instead of failing, set --show-statistics to avoid the
confusion.

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: document the --test mode of operations

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: remove scary message string

The string is no longer used and can be removed.

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: add unitest for crushtool --show-bad-mappings

Signed-off-by: Loic Dachary <loic@dachary.org>
crush: implement --show-bad-mappings for indep

Support the presence of ITEM_NONE device numbers in the indep mapping as
proof of a bad mapping. Implement the associated unit tests.

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #923 from dachary/wip-crush-test

CrushTester patches and documentation

Reviewed-by: Sage Weil <sage@inktank.com>