labs: increase RAM allocation for compute node

Running a default instance on the compute node uses 512 MB RAM, which is
all of the compute node's RAM.

This patch increases the RAM allocation for the compute node to 1024 MB,
enabling it to run an instance.

Change-Id: I59ef85b2680f8b68d08108d738e03a964457680c
Merge "labs: increase RAM allocation for compute node"