Omit service account generation when not using strimzi (#53)

[khorshuheng]

Addresses #53.

In this PR, i generate the service account dynamically, rather than using a user input as originally discussed in issue 53. If we rely on user input, the helm chart will fail if it is executed twice under different helm release name, as the service account would have already existed.

[seglo]

Thanks for the PR. Good point regarding the name of a service account. Can you please add a reference to this configuration in the README.md?

[khorshuheng]

I have added example usage.

[seglo]

Thanks @khorshuheng, but I meant could you add a reference to this configuration option to the configuration table in the README.md (https://github.com/lightbend/kafka-lag-exporter/#configuration-1)

[khorshuheng]

Thanks @khorshuheng, but I meant could you add a reference to this configuration option to the configuration table in the README.md (https://github.com/lightbend/kafka-lag-exporter/#configuration-1)

That is for standalone installation configuration. Service account generation seems to be helm specific, and not applicable to standalone installation?

[seglo]

@khorshuheng My mistake, you're correct. I would like to expand the configuration on the README.md to include a reference for Helm, but indeed that's not currently the case.

Thanks for the contribution!