Added version check for provider/driver backwards compatibility

salt/files/cloud.providers.d/ec2.conf

   location: eu-west-1
   availability_zone: eu-west-1a
   ssh_username: ubuntu
+  {%- if grains.saltversioninfo[0] >= 2016 or (grains.saltversioninfo[0] >= 2015 and grains.saltversioninfo[1] >= 8) %}
   driver: ec2
+  {%- else %}
+  provider: ec2
+  {%- endif %}
 {%- endif %}

salt/files/cloud.providers.d/gce.conf

     master: {{ cloud.get('master', 'salt') }}
   grains:
     test: True
+  {%- if grains.saltversioninfo[0] >= 2016 or (grains.saltversioninfo[0] >= 2015 and grains.saltversioninfo[1] >= 8) %}
   driver: gce
+  {%- else %}
+  provider: gce
+  {%- endif %}
 {%- endif %}

salt/files/cloud.providers.d/rsos.conf

   compute_name: cloudServersOpenStack
   protocol: ipv4
   compute_region: {{ region }}
+  {%- if grains.saltversioninfo[0] >= 2016 or (grains.saltversioninfo[0] >= 2015 and grains.saltversioninfo[1] >= 8) %}
   driver: openstack
+  {%- else %}
+  provider: openstack
+  {%- endif %}
   user:  {{ cloud.get('rsos_user', 'DEFAULT') }}
   tenant: {{ cloud.get('rsos_tenant', 'DEFAULT') }}
   apikey: {{ cloud.get('rsos_apikey', 'DEFAULT') }}

salt/files/cloud.providers.d/saltify.conf

 {% set cloud = salt['pillar.get']('salt:cloud', {}) -%}
 
 saltify:
+  {%- if grains.saltversioninfo[0] >= 2016 or (grains.saltversioninfo[0] >= 2015 and grains.saltversioninfo[1] >= 8) %}
   driver: saltify
+  {%- else %}
+  provider: saltify
+  {%- endif %}
   minion:
     master: {{ cloud.get('master', 'salt') }}