Update sysctl.py

Bugs fixed for the test conditions:
1. Corrected if-else logic, for already correct sysctl option setup before.
2. Added test logic: If state file is trying to setup invalid sysctl option, that is not supported by the minion's kernel.
Update sysctl.py
Merge pull request #5731 from mlister2006/develop

Bugs fixed for the test conditions for states.sysctl