common/cmdparse: emit proper json

common/cmdparse: emit proper json

Instead of '"req": "false"', emit '"req": false'.  Same for conditional.

Luckily, the clients don't really care about this change, as
ceph_argparse.py argdesc interpets the JSON like so:

            self.req = req in (True, 'True', 'true')
            self.positional = positional in (True, 'True', 'true')

Clean up command definitions to use lowercase 'false', but tolerate
both for backward compat during upgrade and to tolerate future errors.

Signed-off-by: Sage Weil <sage@newdream.net>