If circumstances are such that the reweight function believes
OSD disks have zero size, refrain from reweighting OSDs to 0.
This can happen if OSDs are deployed with the noup flag set.
Also move the setting and unsetting of flags above this
calculation as an additional precautionary measure.
Change-Id: Ibc23494e0e75cfdd7654f5c0d3b6048b146280f7
f1e9a6ba83