Bug 1401084

Description of problem:

Feedback from pstodulk on #1295312

(https://bugzilla.redhat.com/show_bug.cgi?id=1295312#c6)

use of redhat-upgrade-tool command in section 1.1.2
  is unlucky, because reader could really do that before he will use preupg
  - maybe there could be some notice or something, that run of preupg before
    inplace-upgrade is neccesary
  - the better option should be maybe write this notice into the section 1.1.4

- 1.1.3.1 - I am not familiar with sattelite but there is mention only: 
    rhn-channel --add --channel rhel-x86_64-server-extras-6
  Shouldn't be there even:
    rhn-channel --add --channel rhel-x86_64-server-optional-6
  ??
  - I am not familiar with repos in satellite, so I am really just asking.
    It's possible that it shouldn't be there.

- 1.1.4
  - 3)
      - as mentioned above, it would be --enablerepo mentioned here
      - I don't see mentioned anywhere, that old RHEL 6 packages are not
        supported on RHEL 7. Maybe we could mention that redhat-upgrade-tool
        has option "--cleanup-post", so old RHEL 6 packages should be removed
        automatically
    
  - 6) that's not completely truth. Not only for items marked as FIXED.
       There exists even postupgrade scripts for modules marked as
       need_inspection or need_action. I guess that text could be
       reformulated. Maybe just something like:
         Perform any post-upgrade tasks planned by Preupgrade Assistant
         modules.
       Could someone else formulate it better? It's just quick idea.

  - 7) In output you see:
>      Red Hat Enterprise Linux Server release 7.0 (Maipo)
       That's just littleness but 7.3 would be better when we update the
       article.