fix(examples/panorama_standalone): Deploy panorama without specifying log_disks

[pavelrn]

Description

Allow examples/panorama_standalone to be used without log_disks input parameter.

Motivation and Context

Without this adjustment examples/panorama_standalone ends with an error when the example is used with out of the box parameters.

How Has This Been Tested?

Test performed as described in README -> Build.

Screenshots (if appropriate)

n/a

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes if appropriate.
• [x] All new and existing tests passed.

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[welcome-to-palo-alto-networks[bot]]

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