Enusre to download sources in cliClient
    
    cliClient is the better place to call cliClient.sources to download sources
    files. This makes it easier for downstream client tool to extend
    cliClient.sources and no need to overwrite related methods to use the
    extension, where the related methods are compile, install, prep, local and
    srpm.
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>