Always included installed state in nodes, even if false

Previously the node data included installed "true" when a node was flagged
installed, but entirely omitted the data if it was false.  Since this is an
important piece of information regardless of whether the flag is set or not,
it should also always be reported.

https://tickets.puppetlabs.com/browse/RAZOR-189
Signed-off-by: Daniel Pittman <daniel@rimspace.net>