mon: osd pool set syntax relaxed, modify unit tests

The argument is no longer restricted to a numerical value. Another
variable was added ( hashpspool ) check that it is a valid variable.

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #717 from dachary/master

mon: osd pool set syntax relaxed, modify unit tests

Reviewed-by: Sage Weil <sage@inktank.com>