Add support for the Packet features:
* phone home - after provisioning is ready, an empty HTTP POST request
is performed to the phone_home_url
* post user password - a random password is generated for the default
user, the password gets encrypted using the encryption public SSH key
and posted to the phone_home_url
Change-Id: Ib3e405b6b5bb4ca65d047c756513b9d6f87cf6de