Description of problem:
Give clear error message when creating an no-auth iscsi-direct pool by using authentication target lun

Version-Release number of selected component (if applicable):
libiscsi-1.18.0-5.module+el8+2173+537e5cb5.x86_64
libvirt-4.9.0-1.module+el8+2241+fdba4e12.x86_64
qemu-kvm-2.12.0-41.el8+2104+3e32e6f8.x86_64

How reproducible:
100%

Steps to Reproduce:

1. Prepare a target lun with authentication=1
...
o- iqn.2017-12.com.virttest:emulated-iscsi-noauth.target2............ [TPGs: 1]
    o- tpg1 .................................. [gen-acls, tpg-auth, 1-way auth]
      o- acls ..................................... [ACLs: 0]
      o- luns .................................. [LUNs: 1]
      | o- lun0 ................................ [fileio/test-ISCSI-2 (/var/lib/libvirt/images/test-iscsi-2.img) (default_tg_pt_gp)]
      o- portals .......................................... [Portals: 1]
        o- 0.0.0.0:3260 ........................................ [OK]
...

2. Create a iscsi-direct pool.
# cat pool.xml
<pool type="iscsi-direct">
  <name>virtimages</name>
  <source>
    <host name="**IP**"/>
    <device path="iqn.2017-12.com.virttest:emulated-iscsi-noauth.target2"/>
    <initiator>
       <iqn name='iqn.1992-01.com.example:client'/>
    </initiator>
  </source>
</pool>
# virsh pool-create pool.xml 
error: Failed to create pool from pool.xml
error: internal error: Failed to logout: Failed to start logout() Trying to logout while not logged in.

Actual results:
As step2

Expected results:
Give a clear error info, such as:
Login Failed. Failed to log in to target. Status: Authentication failure(513)

Additional info:
2018-12-07 09:14:04.920+0000: 25509: error : virISCSIDirectReportLuns:360 : internal error: Failed to reportluns: Failed to send ReportLuns command
2018-12-07 09:14:04.920+0000: 25509: error : virISCSIDirectDisconnect:400 : internal error: Failed to logout: Failed to start logout() Trying to logout while not logged in.