run with bash as the default shell for tests so source command works

tests/ansible/ansible.cfg

@@ -13,6 +13,7 @@ module_utils = lib/module_utils
 retry_files_enabled = False
 display_args_to_stdout = True
 forks = 100
+executable = /bin/bash
 
 # We use lots of deprecated functionality to support older versions.
 deprecation_warnings = False