MFC r277340, r277349:

Remove dead code.
After the ext2 variant of the "orlov allocator" was implemented,
the case for a negative or zero dirsize disappeared.

Drop the dead code and unsign dirsize given that it can't be
negative anyways.

ext2fs: fix for uninitialized pointer read.
path.ep_bp was being used uninitialized in ext4_ext_find_extent().

CID: 1062344
CID: 1008669