common/rc: teach _require_xfs_io_command accept multi-parameters

common/rc: teach _require_xfs_io_command accept multi-parameters

The $param can't be used for all command's options, for example
"help pwrite" include:

 -Z N -- zeed the random number generator (used when writing randomly)
         (heh, zorry, the -s/-S arguments were already in use in pwrite)

We should make param="-Z N", not only "-Z". After this patch, we can
run this function as:

  _require_xfs_io_command pwrite -Z N

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>