[TRI-1379] Some requests to sources/http/$id are failing

[matt-aitken]

Sometimes a request to /api/v1/sources/http/$id is failing to produce a response, and also failing to be stored and then go on to trigger a Run.

Example log: POST /api/v1/sources/http/clnerqc1203e7mw37qa9vlveo - - - - ms

A good response looks like this: POST /api/v1/sources/http/clnerqc1203e7mw37qa9vlveo 200 - - 14.209 ms

We first need to add some better logging and catching to determine what's happening here.

_TRI-1379