Previously there was no way to do a 'dry run' against a set of inventory
configuration files without actually writing the full inventory
structure to disk.
This change adds a simple check flag to the script, allowing users to
pre-validate their configurations prior to executing the Ansible
playbooks. No syntax validation happens against the YAML files; rather,
the dynamic_inventory.py script is executed and builds a full inventory
in memory, but does not write any output.
Currently, this is meant as a starting point. Further validation can
build from here, but the flag is largely meant to check for known
exceptions/errors early.
Change-Id: Ic58566ee124c824c8bba549ade46bce5c268905a
d68e65bfdd