Revert "testing/testcase: use realpath to compare paths"

This reverts commit 49ec3ece.

That commit revealed that all the rpath check was not effective and that
we have in fact lots of components which use system libraries.

We'll fix rpath on slapos profiles and only then we'll fix this check,
to prevent test failures (even if the test failures show a real problem)

slapos/testing/testcase.py

@@ -268,7 +268,6 @@ def checkSoftware(slap, software_url):
     Only libraries from `valid_paths_for_libs` are accepted.
     Returns a list of error messages.
     """
-    valid_paths_for_libs = [os.path.realpath(x) for x in valid_paths_for_libs]
     executable_link_error_list = []
     for path in paths_to_check:
       for root, dirs, files in os.walk(path):