app_python3: fix kemi function call argument type checks

[kmduk]

Pre-Submission Checklist

• Commit message has the format required by CONTRIBUTING guide
• Commits are split per component (core, individual modules, libs, utils, ...)
• Each component has a single commit (if not, squash them into one commit)
• No commits to README files for modules (changes must be done to docbook files
  in doc/ subfolder, the README file is autogenerated)

Type Of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)

Checklist:

• PR should be backported to stable branches
• Tested changes locally
• Related to issue #XXXX (replace XXXX with an open issue number)

Description

The kemi function argument type checks before the arguments are extracted from the python tuple were not strict enough, resulting in the wrong value being passed to the functions.

[miconda]

@kmduk - thanks, can you check and make also a PR for app_python if it needs support for nsss functions?

[aalba6675]

LGTM