WebStyle: memory leak fix in session handling
- Avoids causing a memory leak in handling session when handling legacy mod_python publisher pages.
- By fixing the memory leak, indirectly restores the 'become user' functionality that was broken since a39d0a5539f1200b8f00182ce662a12da95cd472.
- Fixes spurious URL argument rand. (closes #571)
Co-authored-by: Tibor Simko <tibor.simko@cern.ch>