LU-1337 llite: kernel 3.1 changes open_to_namei_flags

LU-1337 llite: kernel 3.1 changes open_to_namei_flags

Kernel 3.1 changes the translation from open_flag to namei_flag,
(kernel commit 8a5e929dd2e05ab4d3d89f58c5e8fca596af8f3a).

So after 3.1, kernel's nameidata.intent.open.flags is different
with lustre's lookup_intent.it_flags, as lustre's it_flags'
lower bits equal to FMODE_xxx while kernel doesn't transliterate
lower bits of nameidata.intent.open.flags to FMODE_xxx.

This patch keeps lustre it_flags' semantics and add
ll_namei_to_lookup_intent_flag for translation.

Signed-off-by: Liu Xuezhao <xuezhao.liu@emc.com>
Change-Id: I408685040688bae574d04cf288abb6ca967607df
Reviewed-on: http://review.whamcloud.com/3583
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>