[OSSM-5564][hack] Fix install testing demo script to support OSSM 2.5

[mkralik3]

Describe the change
Fix autoinjection for bookinfo and sleep demo projects when using with OSSM

Due to this change 997f544 , the bookinfo script doesn't use ENABLE_INJECTION anymore, however, it is needed in prepare_maistra function.

Also, ISTIO_NAMESPACE env is needed in prepare_mainstra function so it was added to install-sleep-demo.sh script. (in version 1.65, the sleep installation was a part of install-testing-demos.sh where the ENV was available)

Issue reference
https://issues.redhat.com/browse/OSSM-5564

[jmazzitelli]

This looks good to me, but I don't use these scripts so I would like someone else to also review this as well.

Also, this PR is targeting the v1.73 branch. We will need another PR to cherry pick this over to the master branch as well to keep everything in sync.

[mkralik3]

@jmazzitelli @ScriptingShrimp
Do we need to backport into master? If I understand correctly, all Maistra stuff were removed from a master branch by #6819, weren't they? This PR is also related only to Maistra. (the root cause is in prepare_maistra function)

[jmazzitelli]

I don't see anything here that is specifically related to Maistra (at least nothing explicitly indicating maistra is required here).

If that is true, we would want this in master if only to keep these files in sync as best we can, and thus avoid potential git conflicts in the future if we ever need to make changes that need backporting.

But with that said, if ALL of this is simply to support Maistra, and this code isn't really used outside of, say, some "IF Maistra THEN" code block somewhere, then we can avoid putting it in master.

[jmazzitelli]

Merging this. @mkralik3 cherry pick what you think is best to the master branch, if anything.

[ScriptingShrimp]

demo apps installed on OCP with OSSM2.5 OK 👍

[mkralik3]

@jmazzitelli I think only this line is worth to backport. I will include it in backport for this #6938