libceph: make abort_on_full a per-osdc setting

The intent behind making it a per-request setting was that it would be
set for writes, but not for reads.  As it is, the flag is set for all
fs/ceph requests except for pool perm check stat request (technically
a read).

ceph_osdc_abort_on_full() skips reads since the previous commit and
I don't see a use case for marking individual requests.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>