... instead of documenting the supported values, so that more explicit
error is presented to users.
Also drop redundant description about the default values. The default
values are added to sample config files generated, so don't have to
be explained in help texts.
Change-Id: I12b201da3e742b55f6cfcf71bdd4413cbf3ee4e5
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>