Avoid unpacking kernel twice when running tests

The general unpack target does need to unpack the kernel for l3docstrip, but 
once that is done there is a copy available in the appropriate place. Thus the
'internal' bundleunpack can then be used for the 'real' unpacking of the
current module files.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4849 de43f980-851b-0410-b2f7-c40aca1f87e0