sstableloader usage string does not require host (nodes)

[tzach]

Running sstabeloader without a host, the following usage is returnes:

> sstableloader a-dir
Initial hosts must be specified (-d)
usage: sstableloader [options] <dir_path>

The usage string does not require host, which seems to be required Should be

usage: sstableloader -d nodes [options] <dir_path>