target: remove initiatorname field in se_acl_lun

From: Chris Zankel <czankel@purestorage.com>

The initiatorname field in se_acl_lun is only a copy of the same field
in se_node_acl, so remove it and use the version in se_node_acl where
needed (it's actually only used for pr_debug)

Signed-off-by: Chris Zankel <czankel@purestorage.com>
Signed-off-by: Spencer Baugh <spencer.baugh@purestorage.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>