Fix EZP-21797: Support recursive sudo usage

JIRA: https://jira.ez.no/browse/EZP-21797

On certain conditions, PAPI will attempt to use sudo recursively (f.e. when using a legacy slot in sudo operation, as described in related JIRA).

This effectively removes the exception, implementing instead a "nesting level" counter instead (similar to transaction counter).

Comments / feedback welcome.
`$sudoNestingLevel` ?