support azure loadbalancer standard sku (#4150) (#4476)

add the support of the folling property in azure-credential-check.yml
  - azure_loadbalancer_sku: Sku of Load Balancer and Public IP. Candidate values are: basic and standard.
  - azure_exclude_master_from_standard_lb: excludes master nodes from standard load balancer.
  - azure_disable_outbound_snat: disables the outbound SNAT for public load balancer rules
  - useInstanceMetadata: Use instance metadata service where possible
  - azure_primary_availability_set: (Optional) The name of the availability set that should be used as the load balancer backend

roles/kubernetes/node/tasks/azure-credential-check.yml

@@ -53,3 +53,20 @@
   fail:
     msg: "azure_route_table_name is missing"
   when: azure_route_table_name is not defined or azure_route_table_name == ""
+
+- name: check azure_loadbalancer_sku value
+  fail:
+    msg: "azure_loadbalancer_sku has an invalid value '{{azure_loadbalancer_sku}}'. Supported values are 'basic', 'standard'"
+  when: azure_loadbalancer_sku not in ["basic", "standard"]
+
+- name: "check azure_exclude_master_from_standard_lb is a bool"
+  assert:
+    that: azure_exclude_master_from_standard_lb |type_debug == 'bool'
+
+- name: "check azure_disable_outbound_snat is a bool"
+  assert:
+    that: azure_disable_outbound_snat |type_debug == 'bool'
+
+- name: "check azure_use_instance_metadata is a bool"
+  assert:
+    that: azure_use_instance_metadata |type_debug == 'bool'