[DO NOT MERGE][CLOUD-2453][KEYCLOAK-7098] Add wait_for_service launch script routine

[iankko]

Describe and add example values for the newly introduced SERVICE_WAIT_NAME,
SERVICE_WAIT_RETRY_MESSAGE, and SERVICE_WAIT_INTRO_MESSAGE environment
variables

Also move the description of SSO_ADMIN_USERNAME, SSO_ADMIN_PASSWORD,
SSO_SERVICE_USERNAME, and SSO_SERVICE_PASSWORD variables from image.yaml
to os-sso/module.yaml. These variables aren't used / referenced outside
of some of os-sso, os-sso71, and os-sso72 modules, and for the future
we want one common 'os-sso' module, sharing all the parts common to
all RH-SSO images. This move is part of such unification

Signed-off-by: Jan Lieskovsky jlieskov@redhat.com

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[iankko]

@rcernich @Crumby PTAL (once got a chance)

Thank you, Jan

[iankko]

The PR was updated, and should be ready for re-review.

[rcernich]

I'm okay with these, but I have to say again that the paradigm is to let the pod cycle until the db becomes available (i.e. this isn't very cloudy, maybe it's sunshiny;)).