BUG: Fix convenience method slicer.util.modulePath introduced in r22851

Since "eval" is executed in the context where it is called, the 'slicer'
module should be imported.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22853 3bd1e089-480b-0410-8dfb-8563597acbee