Reevaluate use of getcwd in python code

[bpkroth]

There are several places where getcwd is used to compose a path assuming that the script is executed from the source/Mlos.Python directory or else used to create a temporary file.

For the first, we should change it to be relative to the file referencing it so that the script can be executed from a different directory.

For the second, we should be using the system provided get temp files to avoid security issues.

[bpkroth]

Here's an example: b47737a