NIFI-9896: Fixed bug with overwriting Script Body value in InvokeScriptedProcessor

[mattyb149]

Description of PR

NIFI-7012 introduced a bug where the Script Body property was populated/overwritten when the Module Directory property changes (which gets called on startup). Since setting the module variable at that point is moot, the faulty code was simply removed. Because of the order of operations of the mock objects, no unit test could be written to illustrate the issue, but it is easily reproduced by setting/changing the Module Directory property on an instance of InvokeScriptedProcessor and Applying the change. It will show as invalid with an error related to trying to parse the script which has been overwritten with the Module Directory value instead.

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