Update RTSP examples to access camera credentials from environment variables.

[rjhowell44]

The RTSP python examples -- like all examples -- should be checked on every release. In their current form, however, they require valid admin/password credentials to connect to RTSP cameras and for this reason have been omitted in the release regression.

Need to update the examples to get the credentials from local environment variables which can be set by automation... without having to have the credentials hardcoded in the script as they are now.