Add --fs-type option to the 'disk' and 'osd' commands

Signed-off-by: Benoît Knecht <benoit.knecht@fsfe.org>
Fix typo in exception message

Signed-off-by: Benoît Knecht <benoit.knecht@fsfe.org>
Merge pull request #85 from BenoitKnecht/master

Add --fs-type option to the 'disk' and 'osd' commands
make sure to user cluster when specified

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
Merge pull request #86 from alfredodeza/6288

make sure to user cluster when specified