Item12515: Bypass ConfigurePlugin hack

Configure makes some effort now to prevent Foswiki from loading (and
corrupting) the configuration hash.  Configure sets two globals:
configureRunning and configureFork.    Normally only configureRuning is
set. If a checker or other routine accidentally causes Foswiki.pm to
load, it will Carp::confess that it was loaded.

When configure actually needs to load Foswiki.pm for example to test
that the module loads, it sets configureFork and also sets
$Foswiki::cfg{ConfigurationFinished}.   This allows Foswiki.pm to load,
and prevents Foswiki::Configure::Load from overlaying the configuration
hash.

However this means that isValid is not set, since Foswiki::Configure::Load
didn't really complete, and Foswiki.pm attempts to load ConfigurePlugin
to resolve the issue.

git-svn-id: http://svn.foswiki.org/trunk/core@17204 0b4bb1d4-4e5a-0410-9cc4-b2b747904278