osd/OSDMap: include pg_temp count in summary

osd/OSDMap: include pg_temp count in summary

It is useful to know how big the pg_temp map is.  Strictly speaking
this is part of the OSDMap so I'm including it here.  It looks like
this:

     osdmap e25: 3 osds: 3 up, 3 in; 1 remapped pgs

It might be more user-friendly to put it in a line with the pgmap
somewhere (where other pg counts are included), but it doesn't quite
fit there either.  So sticking with where it lives in the data
structure!

Signed-off-by: Sage Weil <sage@redhat.com>