[SCSI] libfcoe: FIP link keep-alive should continue while logged off

A check in fcoe_ctlr_send_keep_alive() returns if there's no
port_id for the local port.  This could miss a keep alive if
we just did a host reset and have logged off and will log back in.

Return only if we are doing the port keep alive, in which case
we need to be logged in.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>