[Bug] Water leak sensor appearing twice after update
**Describe the bug**
In v0.0.9 support for Gas detection sensors was added (`gas`). Because there doesn't seem to be a service/characteristic predefined in HomeKit for these kind of sensors, it is exposed as a "Leak Sensor" (just like a real water leak sensor).
For this part of the code changed, which results in there being two waterleak sensors after updating to v0.0.9.

A workaround would be to throw away all the existing accessories, but I'd rather not do that and it should be rather easy to fix.

**To Reproduce**
Steps to reproduce the behavior:
1. Install v0.0.8 and add a waterleak sensor.
2. Upgrade to v0.0.9.

**Expected behavior**
Single water leak sensor accessory would be shown instead of two.

**Versions used**
 - This plugin: 0.0.9
