ReqMgr2 software versions update problem fixed

-the issues comprised from more misconceptions, thus was overall very
    confusing
-first, in order to compare values of dictionaries, these have to be sorted,
    otherwise the order is arbirtary and will -almost- always differ given the
    amount of data of CMSSW versions and ScramArchs
-second, when parsed and JSONified info on CMSSW versions and ScramArchs is
    not logged to stdout (which, since it's a cronjob, gets emailed over) but
    printed into a file straight away, the extra CR, ! or ' ' characters are
    never encountered. Since these characters are really seen in an email sent
    over as the job output, they may be a result of emailing the output or
    simply of some other element different from XML parsing and/or DOM
    building.
    This false idea (as summarised on #4715) was propped up by someone's
    former comment in the code:
        "Somehow we can get extraneous ('\n') text nodes in certain versions
        of Linux"
    this is either something completely different or the same false
    understanding based on the "log output" received in an email.

Although using JSON URL source from tag collector may be advantageous for some
other reasons, XML resource works fine as observed lately in a private VM
setup.

Fixes #4715
Merge pull request #4723 from zdenekmaxa/reqmgr-softwareupdatefix

ReqMgr2 software versions update problem fixed