Add !requiretty to sudoers config in install document
Add !requiretty to sudoers config in install document

When we use devstack to start ironic-inspector service, it starts
sucessfully because we have a tty in devstack screen. But when we try
to use service command to start it, we should add '!requiretty'in the
suoders config, or it will fail.

Change-Id: I1f9f539c8eafea726ca7015ef86773e26a5a5641

openstack/ironic-inspector,openstack/ironic-inspector