Replace bash script with wrapper around ciecplib's ecp-get-cookie

This MR completely replaces the internal logic in the ecp-cookie-init script with a python module that presents the same user interface and munges arguments into a call out to ecp-get-cookie from CIECPLib.

The accompanying tests should be enough to check that most of the arguments are translated properly, but we probably want something that can actually test generating real cookies.

@satyanarayan.raypitambarmohapatra and/or @warren-anderson should give this a spin before accepting anything.