cli: "help add" fails to format the error when number of provided args in incorrect

'help add' command for gluster-related entities like glustervolume and brick does not work. The following error is seen -
(connected)]# help add glustervolume
unknown error: not enough arguments for format string

Change-Id: I48b8880078bb2f9c035b5325af60366bf1c94ae1
Bug-Url: https://bugzilla.redhat.com/922018
Signed-off-by: Ravi Nori <rnori@redhat.com>