mds: move the inos 1,2 and 3 macros to ceph_fs.h

mds: move the inos 1,2 and 3 macros to ceph_fs.h

For inos 1 and 2 there has two places are defining them, to make
sure we won't miss any one of them, let's define them in only one
header file.

Fixes: https://tracker.ceph.com/issues/50216
Signed-off-by: Xiubo Li <xiubli@redhat.com>
(cherry picked from commit 8615807237458e8cebf9497a7431097cdc56c784)

Conflicts:
	src/client/Inode.h
	src/mds/CInode.h
	src/mds/MDCache.cc
	src/mds/Server.cc
        src/mds/SnapServer.h
- change MDS_INO_ROOT to CEPH_INO_ROOT in src/mds/SnapServer.h (nautilus-only)