Squelch duplicate HTTP packet loss error messages

[andrewkroh]

Each time a gap is detected a new error message is appended. One message is
sufficient to know that packet loss occurred so stop adding errors after the first.

I was seeing events with many errors.

   "error": {
         "message": [
           "Packet loss while capturing the response",
           "Packet loss while capturing the response",
          ....
          ]
   }

[adriansr]

LGTM

[andrewkroh]

jenkins, test this