Add GA related parameters to trove-taskmanager.conf.sample

Adds placeholders for 'guest_config' and 'cloudinit_location'
to trove-taskmanager.conf.sample

Fixes bug: 1237395

Change-Id: I5214f5fcc785d94b5b2b60dead316768980d7909
Merge "Add GA related parameters to trove-taskmanager.conf.sample"