osd: During recovery, pass "for_recovery" when attempting re-reads

osd: During recovery, pass "for_recovery" when attempting re-reads

get_all_remaining_reads() is used for two purposes:

1. If a read unexpectedly fails, recover from other shards.
2. If a shard is missing, but is allowed to be missing (typically
   due to unequal shard sizes), we rely on this function to return
   no new reads, without an error.

The test failure we saw case (2), but I think case (1) is important.

Most of the time we probably would not notice, but if insufficient redundancy
exists without the for_recovery being set, then this will result in
recovery failing.

Signed-off-by: Alex Ainscow <aainscow@uk.ibm.com>
(cherry picked from commit 7ab0588ad2853030bf0e716a5f887e0fe714b314)