PE-2352: update puppet node_gce to use GCE v1 API

This patch updates puppet node_gce command to use the latest version
of the GCE API - v1.
The v1 of the API deprecates kernel images and scratch boot disks.
To compensate for that newly each GCE VM instance needs to have
permanent boot disk configured which must contain a kernel and
a booloader capable of booting the kernel in much the same way as
on a real hardware.
To keep up with the changes the pupet node_gce create command now
creates a persistent disk out of the image specified with the --image
option which is then used as the boot disk for the newly created
instance.
Conversely when an instance is being deleted using the
puppet node_gce delete command a check is made to see if it has
a persistent boot disk configured and if it has then the disk is
deleted along with the instance.