testing/testcase: check executables are not linked with system libraries
Except a short whitelist of system libraries, we should have always set rpath so that the slapos version of the library is used. We had issues with components which where compiled with slapos version of openssl but linked without rpath. At runtime they were using system openssl. Rewrite our complex grep shell pipeline in python, with a function parsing ldd output so that we can check not only for not found dynamic libraries, but also for libraries that are found outside of slapos library dirs. This also fixes problems that this grep pipeline did not support paths with spaces in their names.