SdlTransport.handleTransportError() is not thread safe

[chenbd]

SdlTransport.handleTransportError() may be called from different thread.
in handleTransportError(), _transportListener.onTransportError() will be called which cause _transportListener need consider synchronized and may cause some issues.

guess _transportListener's call back should be called in dedicated thread.

https://github.com/smartdevicelink/sdl_android/blob/develop/sdl_android_lib/src/com/smartdevicelink/transport/SdlTransport.java#L103-L107