Improve log messages during iSCSI login failures (specially related to iSCSI redirection)

[Fabio Augusto Miranda Martins]

When an iSCSI Storage (eg.: SolidFire) uses iSCSI redirects, the initial login fails, but it just logs "Login authentication failed with target", while the tcpdump actually shows what exactly was happening. For example:

1. Ubuntu tries to login to the Target IP (10.5.0.26):
24 8.858756 10.5.0.7 10.5.0.26 iSCSI 252 Login Command

2. The Storage (10.5.0.26) replies with:
27 8.860318 10.5.0.26 10.5.0.7 iSCSI 148 Login Response (Target moved temporarily)

The iSCSI packet contains "TargetAddress=10.5.0.18:3260", which is the new iSCSI Portal that we should use:

3. Ubuntu then tries to login to the new portal:
50 9.377491 10.5.0.7 10.5.0.18 iSCSI 252 Login Command

4. Which succeeds:
57 9.379082 10.5.0.18 10.5.0.7 iSCSI 156 Login Response (Success)

But in /var/log/syslog, the only message that is displayed is:

Jan 22 16:01:52 xenial-initiator iscsid: Login authentication failed with target iqn.1993-08.org.debian:01:4df860e415a6:redirect

As an enhancement request, it would be good to see the login redirection being logged into syslog. The same behavior applies to Trusty, Xenial and Bionic.

The same request has been made upstream, but it has been considered low priority so far: https://github.com/open-iscsi/open-iscsi/issues/117