Use different names for USB/CEC and Udev related threads

While debugging some rescanning issues, it helped to distinguish the different PeripheralBus threads. Since there is a limit to thread names, I had to make sure the name fitted into 15 characters.

This is part of a series of PRs: #2323 and #2541

Before:
```
xbmc.bin-+-{EPGUpdater}
         |-{EventServer}
         |-2*[{PVRClient}]
         |-{PVRGUIInfo}
         |-{PVRManager}
         |-2*{PeripheralBus}            <-
         |-{SoftAE}
         |-{TCPServer}
         |-5*[{XBPython}]
         `-8*[{xbmc.bin}]
```

After:
```
xbmc.bin-+-{EPGUpdater}
         |-{EventServer}
         |-2*[{PVRClient}]
         |-{PVRGUIInfo}
         |-{PVRManager}
         |-{PeripBusCEC}                <-
         |-{PeripBusUSBUdev}            <-
         |-{SoftAE}
         |-{TCPServer}
         |-5*[{XBPython}]
         `-8*[{xbmc.bin}]
```