Testing pagerduty service not returning all errors

I was trying to test pagerduty and was using the wrong api key. The problem is that Kapacitor cut off the actual error message returned from PagerDuty so i had no idea what was wrong.

Testing on pagerduty returns:
```
{
"status": "invalid event",
"message": "Event object is invalid",
"errors": [
"Service key is the wrong length (should be 32 characters)"
]
}
```

but testing through Kapacitor only returns:
```
{
"success": false,
"message": "Event object is invalid"
}
```

Start by reproducing the PagerDuty test with an incorrectly sized service key and compare the direct PagerDuty response with Kapacitor's response. Trace the PagerDuty testing entry point and its error-response handling; done means the returned response preserves the PagerDuty errors array as well as the existing message.

Written by the indexing model from the issue text.