prepare_vmware_tests: run test w/ just 1 vcsa (#65433)

Add the ability to run test with just a VCSA instance. This allow us to
test a subset of tests that don't need any ESXi nodes.

test/integration/targets/prepare_vmware_tests/tasks/init_real_lab.yml

@@ -1,8 +1,4 @@
 ---
-- name: load vars
-  include_vars:
-    file: real_lab.yml
-
 - include_tasks: teardown.yml
 
 - when: setup_esxi_instance is not defined

test/integration/targets/prepare_vmware_tests/tasks/main.yml

@@ -5,6 +5,16 @@
     file: common.yml
 
 - when: vcsim is not defined
+  block:
+  - when: esxi1_hostname is not defined and esxi2_hostname is not defined
+    include_vars:
+      file: vcenter_only.yml
+
+  - when: esxi1_hostname is defined and esxi2_hostname is defined
+    include_vars:
+      file: vcenter_with_2_nodes.yml
+
+  - when: vcsim is not defined
     include_tasks: init_real_lab.yml
 
 - when: vcsim is defined

test/integration/targets/prepare_vmware_tests/vars/vcenter_only.yml

@@ -0,0 +1,6 @@
+---
+esxi_hosts: []
+infra:
+virtual_machines: []
+virtual_machines_in_cluster: []
+#esxi_password: ''