Fix hd command so it doesn't error out on EOF

hd would error out on files that were not a multiple of its read
buffer size (4096).  For example:
Read error on init.rc, offset 17040 len 4096, No such file or directory

The fix is to stop reading on EOF instead of treating it as an
error.

Signed-off-by: Scott Anderson <saa@google.com>

(cherry picked from commit a9fac415)

Change-Id: Ib2af725fc39e96c2f81559f61979d451604d4817