Allow the DSB bridge to reuse the object path when multiple interfaces uses the same objectpath

[dotMorten]

Currently if you add multiple interfaces to a device on the DSB, the object path must be unique for each interface. If the path is already used a new path is created with a number as postfix.

Instead if the path is already created, it should be reused, so you can have multiple interfaces on the same objectpath.

I've already done this on my own improved DSB. The changes required can be seen here:
https://github.com/dotMorten/AllJoynDeviceSimulator/pull/2/files

If you think these changes are good, I'd happy to submit a PR with the same changes for this repo as well.

/CC @zhuridartem

[jhutchings1]

Hey Morten,
Thanks for your contributions! Unfortunately, our dev team is heads down on coding right now and won't be able to look at pull requests for the DSB project right now. We'll check back when we've got more bandwidth to validate your changes.

Thanks!