os/bluestore: fix unexpected ENOSPC in Avl/Hybrid allocators.

os/bluestore: fix unexpected ENOSPC in Avl/Hybrid allocators.

Avl allocator mode was returning unexpected ENOSPC in first-fit mode if all size-
matching available extents were unaligned but applying the alignment made all of
them shorter than required. Since no lookup retry with smaller size -
ENOSPC is returned.
Additionally we should proceed with a lookup in best-fit mode even when
original size has been truncated to match the avail size.
(force_range_size_alloc==true)

Fixes: https://tracker.ceph.com/issues/50656
Signed-off-by: Igor Fedotov <ifedotov@suse.com>