Execute a command independantly of the output gathering part of
        sosreport.

def call_ext_prog(self, prog, timeout=300, stderr=True,
                      chroot=True, runat=None):
        """Execute a command independantly of the output gathering part of
        sosreport.
        """
        return self.get_command_output(prog, timeout=timeout, stderr=stderr,
                                       chroot=chroot, runat=runat)