Client example: Use instance logger instead of global logger

[andygrunwald]

The [example_client_test.go](./example_client_test.go) is using two types of logging mechanism:

amqp091-go/example_client_test.go

Line 89 in 21ccfde

log.Println("Attempting to connect")

and

amqp091-go/example_client_test.go

Line 217 in 21ccfde

session.logger.Println("Push failed. Retrying...")

This Pull Request is changing the logging behavior to only use the logging instance inside the session struct

[MirahImage]

Thanks!