libceph: add support for primary_temp mappings

Change apply_temp() to override primary in the same way pg_temp
overrides osd set.  primary_temp overrides pg_temp primary too.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>

diff --cc net/ceph/osdmap.c
Simple merge