xfs_db: use correct inode to set inode type

xfs_db: use correct inode to set inode type

A test fails as:
  # xfs_db -c "inode 133" -c "addr" -c "p core.size" -c "type inode" -c "addr" -c "p core.size" /dev/sdb1
  current
          byte offset 68096, length 512
          buffer block 128 (fsbno 16), 32 bbs
          inode 133, dir inode -1, type inode
  core.size = 123142
  current
          byte offset 65536, length 512
          buffer block 128 (fsbno 16), 32 bbs
          inode 128, dir inode 128, type inode
  core.size = 42

The "type inode" command accidentally moves the io cursor because it
forgets to include the io cursor's buffer offset when it computes the
inode number from the io cursor's location.

Fixes: 533d1d229a88 ("xfs_db: properly set inode type")
Reported-by: Jianhong Yin <jiyin@redhat.com>
Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>