`copr-build` passes extra_args to copr-cli command
    
    The right target for passing extra_args (arguments that are placed
    after '--' on the command line) is the command copr-cli instead
    of rpmbuild command.
    
    Fixes: https://pagure.io/fedpkg/issue/510
    JIRA: RHELCMP-11429
    
    Signed-off-by: Ondrej Nosek <onosek@redhat.com>