Incrase heap size for logstash indexers.

The default java heap size is too small for our logstash indexers.
Double it to 2g. Do this by adding an /etc/default/logstash-indexer file
that the upstart configs source if it is present. This required some
tweaks to the upstart configuration to load the defaults properly.

Co-Authored-By: K Jonathan Harker <k.jonathan.harker@hp.com>
Change-Id: I63447f59f3fa6d466a7d275476121fe8339479dc
Merge "Incrase heap size for logstash indexers."