AOSP: HACK: android: exit(1) if selabel_lookup fails

AOSP: HACK: android: exit(1) if selabel_lookup fails

If selabel_lookup fails, the current implementation of set_selinux_xattr
returns -1, but the command line tool e2fsdroid reports success.
There's a bunch of things wrong:

1) -1 does not appear to be a legal errcode_t value. The appropriate
return value appears to be DIRENT_ABORT.
2) A return value of DIRENT_ABORT is ignored by the upper layers of the
code.
3) Attempting to fix the upper layers of the code to not ignore
DIRENT_ABORT results in complaints about not being able to create
/lost+found.

Call stack:

- main
 - android_configure_fs
  - __android_configure_fs
   - ext2fs_dir_iterate2
    - ext2fs_block_iterate3
     - ext2fs_process_dir_block
      - walk_dir
       - ext2fs_dir_iterate2
        - ext2fs_block_iterate3
         - ext2fs_process_dir_block
          - walk_dir
           - ext2fs_dir_iterate2
            - ext2fs_block_iterate3
             - ext2fs_process_dir_block
              - androidify_inode
               - set_selinux_xattr

I'm honestly not sure how to fix this, so just throw an exit(1) in
there, to make sure the program dies a horrible death if
selabel_lookup() fails. This is much better than the alternative of
e2fsdroid returning success with an improperly labeled file.

Bug: 34358308
Test: Artifically modify selabel_lookup() to return a failure, and
      verify Android doesn't compile.
Test: Verify Android compiles under normal circumstances.
Change-Id: I60e04bc6559a66d3f3202f2c28e2519856385ded
From AOSP commit: 87a7db7cf2ca0feecaccad94bf22f92c726000c3

Signed-off-by: Theodore Ts'o <tytso@mit.edu>