fix: abort branch if child process receives SIGTERM

[rarkins]

Changes:

Detects when child process fails due to SIGTERM and aborts the branch.

Context:

Trying to handle this gracefully as an alternative to:

{
  "level": 20,
  "branch": "renovate/npm-lodash-vulnerability",
  "err": {
    "killed": false,
    "code": null,
    "signal": "SIGTERM",
    "cmd": "docker pull docker.io/renovate/node:latest",
    "stdout": "latest: Pulling from renovate/node\n5d3b2c2d21bb: Pulling fs layer\n3fc2062ea667: Pulling fs layer\n75adf526d75b: Pulling fs layer\n8fac8f7ae834: Pulling fs layer\nbd2f495a6dc9: Pulling fs layer\n5cb6cb04bade: Pulling fs layer\na0d68e40d167: Pulling fs layer\n9bfa22e90d01: Pulling fs layer\n7b5f4722109c: Pulling fs layer\n8fac8f7ae834: Waiting\nbd2f495a6dc9: Waiting\n5cb6cb04bade: Waiting\na0d68e40d167: Waiting\n9bfa22e90d01: Waiting\n7b5f4722109c: Waiting\n3fc2062ea667: Verifying Checksum\n3fc2062ea667: Download complete\n75adf526d75b: Verifying Checksum\n75adf526d75b: Download complete\nbd2f495a6dc9: Verifying Checksum\nbd2f495a6dc9: Download complete\n8fac8f7ae834: Verifying Checksum\n8fac8f7ae834: Download complete\n5d3b2c2d21bb: Verifying Checksum\n5d3b2c2d21bb: Download complete\n9bfa22e90d01: Verifying Checksum\n9bfa22e90d01: Download complete\n",
    "stderr": "",
    "message": "Command failed: docker pull docker.io/renovate/node:latest\n",
    "stack": "Error: Command failed: docker pull docker.io/renovate/node:latest\n\n    at ChildProcess.exithandler (child_process.js:308:12)\n    at ChildProcess.emit (events.js:315:20)\n    at ChildProcess.EventEmitter.emit (domain.js:467:12)\n    at maybeClose (internal/child_process.js:1048:16)\n    at Socket.<anonymous> (internal/child_process.js:439:11)\n    at Socket.emit (events.js:315:20)\n    at Socket.EventEmitter.emit (domain.js:467:12)\n    at Pipe.<anonymous> (net.js:673:12)"
  },
  "type": "npm",
  "msg": "lock file error",
  "time": "2021-03-04T16:41:19.441Z"
}

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please tick one)

I have verified these changes via:

• Code inspection only, or
• Newly added unit tests, or
• No new tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[renovate-release]

🎉 This PR is included in version 24.72.5 🎉

The release is available on:

• GitHub release
• 24.72.5

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