osd/OSDMap: add osd_is_valid_op_target()

Helper to check whether an osd is a given op target for a pg.  This
assumes that for EC we always send ops to the primary, while for
replicated we may target any replica.

Signed-off-by: Sage Weil <sage@redhat.com>
osd/OSD: use OSDMap helper to determine if we are correct op target

Use the new helper.  This fixes our behavior for EC pools where targetting
a different shard is not correct, while for replicated pools it may be. In
the EC case, it leaves the op hanging indefinitely in the OpTracker because
the pgid exists but as a different shard.

Fixes: #9835
Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #2906 from ceph/wip-9835

osd: fix misdirected ec ops stuck in optracker (9835)

Reviewed-by: Samuel Just <sam.just@inktank.com>