btrfs/004: fix failure with inlined file extents

btrfs/004: fix failure with inlined file extents

Files that consist of an inline extent, have the corresponding
data in the filesystem btree and not on a dedicated extent. For
such extents filefrag (fiemap) will report a physical location
of 0 for that extent and set the 'inline' flag.

The btrfs inspect-internal logical-resolve command will cause a
lookup in the extent tree for the extent address we give it as
an argument, which fails with errno ENOENT if it is 0.

This error didn't happen always, as the test uses fsstress to
generate a random filesystem, which needed to generate at least
one file that could be inlined (content less than 4018 bytes).

Example, taken from results/btrfs/004.full:

   # filefrag -v /home/fdmanana/btrfs-tests/scratch_1/snap1/p0/de/d1b/dcb/fb1
   Filesystem type is: 9123683e
   File size of /home/fdmanana/btrfs-tests/scratch_1/snap1/p0/de/d1b/dcb/fb1 is 3860 (1 block of 4096 bytes)
    ext:     logical_offset:        physical_offset: length:   expected: flags:
      0:        0..    4095:          0..      4095:   4096:             not_aligned,inline,eof
      1:      280..     344:      35190..     35254:     65:          1: eof
   /home/fdmanana/btrfs-tests/scratch_1/snap1/p0/de/d1b/dcb/fb1: 2 extents found
   after filter: 0#0#0 0#0#0
   # stat -c %i /home/fdmanana/btrfs-tests/scratch_1/snap1/p0/de/d1b/dcb/fb1
   403
   # /home/fdmanana/git/hub/btrfs-progs/btrfs inspect-internal logical-resolve -P 0 /home/fdmanana/btrfs-tests/scratch_1
   ioctl ret=-1, error: No such file or directory

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>