Get rid of fake-install

Get rid of fake-install

Instead, use $(BUILDTOP)/plugins as the plugin base for tests.  For
each real plugin module, create a link in the parent directory if
we're doing a shared-library build--so built KDB modules can be found
in plugins/kdb, preauth modules in plugins/preauth, etc..

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25436 dc483132-0cff-0310-8789-dd5450dbe970