flasher scripts: add `sim_services` import dependency.

In `simulation-04-00-06-rc`, the module `I3MCEventHeaderGenerator`, which is required by the scripts, probably has been moved to the `sim-services` package. Without this modification the following error would occur:

> FATAL (icetray): Module/service "I3MCEventHeaderGenerator" not registered with I3_MODULE() or I3_SERVICE_FACTORY() (I3Factory.h:83 in FactoryFn I3Factory<Product, FactoryFn>::Create(std::string) const [with Product = I3Module, FactoryFn = boost::function<boost::shared_ptr<I3Module>(const I3Context&)>])

This commit resolves this issue.

The change is also compatible to simulation 3.
Merge pull request #1 from fiedl/master

flasher scripts: add `sim_services` import dependency.