Werk #6595: if.include: Recognize duplicate interface items correctly

The recognition works correct but not in the following situation where the wrong network interface data is checked.

• Use desciption or use alias is configured in the ruleset Network Interface and Switch Port Discovery.
• Two or more network interfaces exist with same description or alias.
• Only one network interface with this description or alias is discovered.
• The discovered network interface does not rank first.

Now the index is attached if an alias or description exists at least twice.

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