iscsid: retry login for ISCSI_ERR_HOST_NOT_FOUND

If a driver is being loaded then the scsi_host might not yet
be added. This has iscsid retry login if the host is not yet
in sysfs.
iscsid: Fix double close of mgmt ipc fd

Ran into a problem where iscsiadm was closing an already closed fd
(returning EBADF. Seems like the close() in line 466 is redundant as
it is done in mgmt_ipc_destroy_queue_task(). Could also assign
qtask->mgmt_ipc_fd to NULL, but it seems better to do it this way.