ORI-360 osd-zfs: cache SA values in osd_object

- cache object attributes in osd_object to avoid SA lookup every time
- use lu_env to store stack values
- protect object attributes with read/write lock
- replace old udmu ASSERT with Lustre LASSERT
- remove unused old udmu code
- add error handling and reporting in code
- all osd and __osd functions returns negative error codes
- use 'rc' instead of 'error' to keep common style

Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: I01c2b443199d12676e081289fcc9789c1e807a16
Reviewed-on: http://review.whamcloud.com/2006
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: Hudson