libceph: check length of osdmap osd arrays

Check length of osd_state, osd_weight and osd_addr arrays.  They
should all have exactly max_osd elements after the call to
osdmap_set_max_osd().

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