LU-15027 sec: initialize ll_inode_info for fake inode

LU-15027 sec: initialize ll_inode_info for fake inode

When creating an encrypted symlink, we need to make use of a fake
inode in order to be able to encrypt the target name before sending
the create request to the MDS.
This fake inode needs minimal initialization, but it is at least
required to properly initialize the ll_inode_info associated with this
fake inode.

Lustre-change: https://review.whamcloud.com/45023
Lustre-commit: 3fb7b6271855c0b12c5a560c7f6287cdda3d1cd6

Fixes: e735298935 ("LU-13717 sec: filename encryption - symlink support")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I20c30d873f9bffdbdc8b5f272cb8b80e5be7fbfb
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45733
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>