LU-1244 obdecho: destroy ost objects for md echo client.

LU-1244 obdecho: destroy ost objects for md echo client.

Since md echo client connects MDT directly, and there are no
lov for echo client, so it will destroy the ost object in
mdd_unlink directly.

In setxattr test, it should set another EA, instead of LOV,
which would cause problem in the following test.

Reset valid before unlink and getattr.

Signed-off-by: Di Wang <di.wang@whamcloud.com>
Change-Id: Id3da42fac4af944ceef7db34f13e8f2b40f733b6
Reviewed-on: http://review.whamcloud.com/2356
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>