Fix issue #260 Dup instance failure on instance enumerate
Fix issue #260 Dup instance failure on instance enumerate

The pywbem mocker compile MOF functions uses the CreateInstance from
pywbem mof_compiler.  This does not test for duplicate instances. See
pywbem issue # 1852.

However, we caused the problem because we duplicated a key in the test
file tests/unit/simple_mock_model_ext.mof

This fixes that key property duplication.

I must be going blind to miss this.

NOTE: Reopened issue # 260 to do this fix

pywbem/pywbemtools,pywbem/pywbemtools