MINIFICPP-2725 python: fix EL with ENVIRONMENT scope

[szaszm]

i.e. evaluation with no FlowFile context

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[lordgamez]

I think this would be more readable:

if flow_file is None:
    if self.is_dynamic:
        new_string_value = self.cpp_context.getDynamicProperty(self.name)
    else:
        new_string_value = self.cpp_context.getProperty(self.name)
else:
    if self.is_dynamic:
        new_string_value = self.cpp_context.getDynamicProperty(self.name, flow_file.cpp_flow_file)
    else:
        new_string_value = self.cpp_context.getProperty(self.name, flow_file.cpp_flow_file)

or maybe even better a shorter version:

if self.is_dynamic:
    getter = self.cpp_context.getDynamicProperty
else:
    getter = self.cpp_context.getProperty

args = () if flow_file is None else (flow_file.cpp_flow_file,)

new_string_value = getter(self.name, *args)