fix duplicate function call of _kill()

[gary837837]

Environments

• os: ubuntu 18.04
• node: v10.14.1
• mirakurun: 2.8.4

When the record process which tuner has the option "dvbDevicePath" was killed, the code

Mirakurun/src/Mirakurun/TunerDevice.ts

Line 306 in ed205a7

this._kill(false);

still be called if the code

Mirakurun/src/Mirakurun/TunerDevice.ts

Line 317 in ed205a7

this._process.once("exit", () => this._exited = true);

execute later than cat.close()