Https is ignored when configured by env var

[ElementalWarrior]

Basically if you configure the endpoint via environment variable, it will always to try communicate via insecure. Because use_ssl_credentials is used in the grpc exporter, but we never set it. And it can be configured via conf file, but only if you don't use the env variable.

[linux-foundation-easycla[bot]]

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• :white_check_mark: login: ElementalWarrior / name: James McDonnell (8631e852fd5ca7b469ac3406799a74c39be4a217)

[ElementalWarrior]

@seemk or @kpratyus or @DebajitDas would someone give a review? I can't be the only one encountering this

[marcalff]

/easycla