Homebridge/plugin upgrades silently fail using .npmrc with environment token
**Describe The Bug:**
If you have an .npmrc file that uses environment substitution than Homebridge and plugin upgrades silently fail.

**To Reproduce:**
1. Create an .npmrc as follows:
```
//registry.npmjs.org/:_authToken=${NPM_TOKEN}
```
2. Try a plugin or homebridge upgrade

Homebridge upgrades will restart the server without performing the upgrade.
Plugin upgrades will display an error in the console window (if you can read that fast), then say that the plugin upgrade succeeded. But the plugin upgrade did not succeed.

**Expected behavior:**
Everything succeeds or if it cannot succeed than it reports the error.

[**Logs:**]
```
Error: Failed to replace env in config: ${NPM_TOKEN}
    at /Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:415:13
    at String.replace (<anonymous>)
    at envReplace (/Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:411:12)
    at parseField (/Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:389:7)
    at /Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:330:24
    at Array.forEach (<anonymous>)
    at Conf.add (/Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:328:23)
    at ConfigChain.addString (/Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/node_modules/config-chain/index.js:244:8)
    at Conf.<anonymous> (/Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/lib/config/core.js:316:10)
    at /Users/matthew/.nvm/versions/node/v14.15.4/lib/node_modules/npm/node_modules/graceful-fs/graceful-fs.js:123:16

**Homebridge Config:**
<!-- Paste relevant output between the two ``` lines below -->
<!-- Remove any sensitive information, passwords, etc. -->

```json
{
    "bridge": {
        "name": "Homebridge AA09",
        "username": "removed",
        "port": 51893,
        "pin": "removed"
    },
    "accessories": [],
    "platforms": [
        {
            "name": "Config",
            "port": 8581,
            "platform": "config"
        },
        {
            "refreshToken": "removed",
            "platform": "Ring"
        },
        {
            "name": "Nest",
            "googleAuth": "removed",
            "platform": "Nest"
        }
    ]
}```

**Environment:**

* **Node.js Version**: 14.6.0
* **NPM Version**: 6.14.11
* **Homebridge Version**: 1.1.7
* **Operating System**: macOS 10.15.7
* **Process Supervisor**: launchctl

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