Not to pass the engine param if present

Change-Id: I841e8d0aad0892fddfd34bfc27936403a46243f6

salt/files/_engine.conf

 
 engines:
 {%- for engine_name, engine in master.engine.items() %}
-- {{ engine.get('engine', engine_name) }}: {{ engine|yaml }}
+{%- set name = engine.get('engine', engine_name) %}
+{%- if engine.engine is defined %}{%- do engine.pop('engine') %}{% endif %}
+- {{ name }}: {{ engine|yaml }}
 {%- endfor %}