scsi: iscsi: Perform connection failure entirely in kernel space

scsi: iscsi: Perform connection failure entirely in kernel space

Connection failure processing depends on a daemon being present to (at
least) stop the connection and start recovery.  This is a problem on a
multipath scenario, where if the daemon failed for whatever reason, the
SCSI path is never marked as down, multipath won't perform the failover and
IO to the device will be forever waiting for that connection to come back.

This patch performs the connection failure entirely inside the kernel.
This way, the failover can happen and pending IO can continue even if the
daemon is dead. Once the daemon comes alive again, it can execute recovery
procedures if applicable.

Cc: Mike Christie <mchristi@redhat.com>
Cc: Lee Duncan <LDuncan@suse.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20200125061925.191601-1-krisman@collabora.com
Co-developed-by: Dave Clausen <dclausen@google.com>
Co-developed-by: Nick Black <nlb@google.com>
Co-developed-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Co-developed-by: Anatol Pomazau <anatol@google.com>
Co-developed-by: Tahsin Erdogan <tahsin@google.com>
Co-developed-by: Frank Mayhar <fmayhar@google.com>
Co-developed-by: Junho Ryu <jayr@google.com>
Co-developed-by: Khazhismel Kumykov <khazhy@google.com>
Reviewed-by: Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Co-developed-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Bharath Ravi <rbharath@google.com>
Signed-off-by: Dave Clausen <dclausen@google.com>
Signed-off-by: Nick Black <nlb@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Anatol Pomazau <anatol@google.com>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: Junho Ryu <jayr@google.com>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>