tests: run some playbooks against only one target.

tests/ansible/integration/ssh/variables.yml

@@ -3,7 +3,7 @@
 # whatever reason.
 
 - name: integration/ssh/variables.yml
-  hosts: test-targets
+  hosts: test-targets[0]
   connection: local
   vars:
     # ControlMaster has the effect of caching the previous auth to the same

tests/ansible/integration/strategy/_mixed_mitogen_vanilla.yml

@@ -2,9 +2,10 @@
 # issue #294: ensure running mixed vanilla/Mitogen succeeds.
 
 - name: integration/strategy/_mixed_mitogen_vanilla.yml (mitogen_linear)
-  hosts: test-targets
+  hosts: test-targets[0]
   any_errors_fatal: true
   strategy: mitogen_linear
+  run_once: true
   tasks:
     - custom_python_detect_environment:
       register: out
@@ -15,8 +16,9 @@
     - assert:
         that: strategy == 'ansible.plugins.strategy.mitogen_linear.StrategyModule'
 
+
 - name: integration/strategy/_mixed_mitogen_vanilla.yml (linear)
-  hosts: test-targets
+  hosts: test-targets[0]
   any_errors_fatal: true
   strategy: linear
   tasks:
@@ -31,7 +33,7 @@
 
 
 - name: integration/strategy/_mixed_mitogen_vanilla.yml (mitogen_linear)
-  hosts: test-targets
+  hosts: test-targets[0]
   any_errors_fatal: true
   strategy: mitogen_linear
   tasks: