Add autodetect option to set-default-security-context flag

[david-kow]

The behaviour of the autodetect flag should be that it will make the operator try to detect whether it's running on OCP. If yes, operator will behave as the set-default-security-context was set to false, otherwise the operator will behave as the set-default-security-context was set to true.

For more context check the discussion in #2791.
The "warning" about this behaviour will be also added to ECK 1.9.0 release notes (check #5062).