os/bluestore: simplify per-pool-stat config options

os/bluestore: simplify per-pool-stat config options

The previous bluestore_no_per_pool_stats_tolerance had a lot of possible
values, not all of which make sense to users.  Replace with a single new
option, bluestore_fsck_error_on_no_per_pool_stats, which controls whether
the lack of per-pool stats is an error or a warning.  On repair, we will
unconditionally convert to per-pool stats.

This brings us in sync with the newer
bluestore_fsck_error_on_no_per_pool_omap.

Note that one part of the ceph_test_objectstore test is dropped since it
is no longer possible to create a store with legacy stats.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 7e96024254d98591a5431623fb355a20f322b554)

 Conflicts:
	PendingReleaseNotes
        - trivial
	src/os/bluestore/BlueStore.cc
        - lacking of int_repaired method