ffmpeg HKSV high cpu usage
**Describe The Problem:**
I'm seeing high CPU usage from ffmpeg and long running processes, without an active video session - I assume HKSV recording is the root cause.  4x Unifi Protect cameras - 2x G4 Pros, 1x G3 instant, 1x G4 Doorbell.  

Maybe ffmpeg keeps running after 'homekit canceled the request'?  If I check timestamps below, I see a start of ffmpeg at 11:36 (aligning with restart + start of buffer).  

```
cemil      22656  216 13.9 3240580 2240388 ?     Sl   11:36  12:01 /homebridge/node_modules/homebridge-unifi-protect/node_modules/ffmpeg-for-homebridge/ffmpeg -hide_banner -f mp4 -i pipe:0 -map 0:v -vcodec libx264 -pix_fmt yuvj420p -profile:v main -level:v 4.0 -preset veryfast -b:v 2000k -bufsize 4000k -maxrate 2000k -force_key_frames expr:gte(t, n_forced * 4) -fflags +genpts -reset_timestamps 1 -movflags frag_keyframe+empty_moov+default_base_moof -map 0:a -acodec copy -f mp4 pipe:1
cemil      22657  339 14.0 3240404 2268164 ?     Rl   11:36  18:53 /homebridge/node_modules/homebridge-unifi-protect/node_modules/ffmpeg-for-homebridge/ffmpeg -hide_banner -f mp4 -i pipe:0 -map 0:v -vcodec libx264 -pix_fmt yuvj420p -profile:v main -level:v 4.0 -preset veryfast -b:v 2000k -bufsize 4000k -maxrate 2000k -force_key_frames expr:gte(t, n_forced * 4) -fflags +genpts -reset_timestamps 1 -movflags frag_keyframe+empty_moov+default_base_moof -map 0:a -acodec copy -f mp4 pipe:1

```
<img width="595" alt="Screen Shot 2022-02-14 at 11 43 59 am" src="https://user-images.githubusercontent.com/834596/153782970-b245a218-7bd5-458e-b5bf-7e04389d0ff6.png">

This is on a fairly robust (i5-12400) system, homebridge hosted via Docker (alpine linux).  

**To Reproduce:**
Unknown root cause - happens upon restart of homebridge, can't replicate what starts/stops these processes.  

**Logs:**
<!-- In order to be helpful, include the relevant logs from Homebridge, if applicable. -->

```
[2/14/2022, 11:36:40 AM] [UniFi Protect] UDM-Pro [UDM-PRO] Garage Doorbell [UVC G4 Doorbell]: Enabling HomeKit Secure Video event recording: 1920x1080@30fps, 2000 kbps with a 4 second timeshift buffer.
[2/14/2022, 11:36:40 AM] [UniFi Protect] UDM-Pro [UDM-PRO] North Lawn Cam [UVC G4 Pro]: Enabling HomeKit Secure Video event recording: 1920x1080@30fps, 2000 kbps with a 4 second timeshift buffer.
[2/14/2022, 11:36:40 AM] [UniFi Protect] UDM-Pro [UDM-PRO] South Lawn Cam [UVC G4 Pro]: Enabling HomeKit Secure Video event recording: 1920x1080@30fps, 2000 kbps with a 4 second timeshift buffer.
[2/14/2022, 11:37:14 AM] [UniFi Protect] UDM-Pro [UDM-PRO] Garage Doorbell [UVC G4 Doorbell]: HomeKit Secure Video has recorded a 29 second motion event.
[2/14/2022, 11:37:14 AM] [UniFi Protect] UDM-Pro [UDM-PRO] Garage Doorbell [UVC G4 Doorbell]: HomeKit Secure Video event recording ended abnormally: HomeKit canceled the request.
```

**Homebridge Configuration:**

```json
{
            "controllers": [
                {
                    "address": "0.0.x.x",
                    "password": "xxx,
                    "username": "yyy"
                }
            ],
            "motionDuration": 7,
            "platform": "UniFi Protect"
        },
```

**Screenshots:**
provided

**Environment:**

* **Homebridge Version:** Homebridge v1.4.0
* **Node Version:** v16.14.0
* **Homebridge-UniFi-Protect Plugin Version:** 5.3.0
* **UniFi Protect Version:** 1.21.0
* **UniFi Protect Controller Type:** UDMP
* **UniFi Protect Controller Firmware Version:** 1.11.0
* **Apple Device and iOS / macOS / iPadOS / tvOS Version:** N/A - but using iPhone 13 Pro on latest firmware, in general.
* **Operating System and OS Version:** Alpine Linux Docker container on Linux Mint host. 

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