osd: set min_read_recency_for_promote to default 1 when doing upgrade

When upgrading from a build without the promotion on 2nd read feature,
should set min_read_recency_for_promote to the default value 1, instead
of 0.

Signed-off-by: Zhiqiang Wang <wonzhq@hotmail.com>
Merge pull request #2444 from wonzhq/read-recency

osd: set min_read_recency_for_promote to default 1 when doing upgrade

Reviewed-by: Sage Weil <sage@redhat.com>