[#56341206] Allow configuration of mongodb version
[#524141] Upstart conf, only when upstart
[#56341206] Allow upstart expects configuration

Defaults to expects daemon which works with the most up to date mongodb
[#56341206] Change fork to false for debian

The fork setting was set to true when rhel was added as a potential
target for this library. This causes issues when using older versions of
mongo with upstart.

As this fixes the need for the 'expect daemon' in the upstart config I
have set the default for the param to false and altered the related
tests.
Merge pull request #1 from alphagov/allow-different-versions

Allow different versions