The old code incorrectly used lbs_cmd_with_response() and now uses
lbs_cmd_async().

While there I noticed that there is no real useful return values for
asynchronous command functions, so I made the function "void".
Signed-off-by: NHolger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: NDan Williams <dcbw@redhat.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>