Sorry, Relativity is NOT a general purpose database.
Its purpose is to access data in COBOL data files from an ODBC application. So, don't expect it to be able to do fancy things like create tables in arbitrary places. The main reason that it creates tables at all is because it was easier to create test cases.
On the bright side, it does NOT create the file's table in the installation directory. It creates them in the same directory as the catalog. So, if you want to create files in the /tmp directory, simply place the catalog there.