LU-14677 llite: move env contexts to ll_inode_info level

LU-14677 llite: move env contexts to ll_inode_info level

Contrary to file, inode is always available, so move the list of
env contexts from the file data to the ll_inode_info level.
This is needed because we will have to handle env properties in
ll_get_context() and ll_xattr_list()/ll_listxattr().
This also requires changing lli_lock from a spinlock to an rwlock.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I478d2a8eabfcb09074ba52601f05840d047a6da2
Reviewed-on: https://review.whamcloud.com/44198
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>