mon: adjust mon-osd-[near]full-ratio on the fly
The nearfull and full ratios are set in the PGMap constructor, and the lists for maintained privatley by PGMap. That means you can't adjust them on the fly when your cluster fills up, which is a useful thing to do!
Either the lists need to be adjusted by PGMonitor class (where g_conf is visible) and rechecked during tick(), or tick() needs to (re)set the ratios in PGMap and PGMap can adjust, or something else along those lines. The conf update callback could be useful here, although a check in tick() would also be sufficient.