Refactor: libpacemaker: Don't use pcmk__formatted_printf...

...in pcmkfence_history. This function can be called for all sorts of
output formats, not just text, so it should not use
pcmkformatted_printf.

Instead, add an extra argument to the stonith-event message that controls
whether this extremely minimal output format will be used. This
argument will always be set if ->is_quiet is true, but only the text
handler will look at it. This should preserve existing output for all
other output formats.