updated to handle a collection

tasks/main.yml

diff --git a/tasks/main.yml b/tasks/main.yml
index 74ab89f..9ea6cb2 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -1,9 +1,9 @@
 ---
 # tasks file for apigee-opdk-set-reachable
-- name: Validate that server_type was provided
+- name: Validate that server_types was provided
   fail:
-    msg: "Please provide the server_type"
-  when: server_type is not defined
+    msg: "Please provide the server_types"
+  when: server_types is not defined
 
 - block:
   - name: Check for {{ server_type }} self report