Don't use a shell builtin: shell builtins aren't available since
'command' ansible module is used. Instead, fail with an explicit
error when the required test_command variable is not set.
Fix this error:
Ansible output: b'failed: [host] (item=exit 1) => {
"ansible_loop_var": "item",
"changed": false,
"cmd": "exit 1",
"item": "exit 1",
"msg": "[Errno 2] No such file or directory: 'exit': 'exit'",
"rc": 2
}
Change-Id: I88303f7302d7354ffc8b18e607b28349a9860a57
0eb09e7b4f