Make rest api timeout configureable.

It is important to be able to increase timeouts on api when running
orchestrate tasks via pepper.

Change-Id: I3ff0988bfec3ec4715348c5de15247fe0b075443

salt/files/_api.conf

   disable_ssl: True
   {%- endif %}
   expire_responses: {{ api.get('expire_responses', False) }}
+  {%- if api.rest_timeout is defined %}
+  rest-timeout: {{ api.rest_timeout }}
+  {%- endif %}
   {%- if api.get('debug', False) %}
   debug: True
   {%- endif %}

tests/pillar/master_api.sls

         formula: {}
   api:
     enabled: true
+    rest_timeout: 7200
     ssl:
       engine: salt
     bind: