Disabled requiretty in cloud-init script

Sahara expects requiretty to be disabled. Usually we disable it in
diskimagebuilder. Disabling it in runtime to be able to use stock
images.

Change-Id: I62bfd6db5ce9cbf6ab3c3a33d0053f0c4166082a
Closes-Bug: #1399052
Merge "Disabled requiretty in cloud-init script"