Improving error handling on price streamers

This fixes the following error:

23:29:32 web.1  | events.js:72
23:29:32 web.1  |         throw er; // Unhandled 'error' event
23:29:32 web.1  |               ^
23:29:32 web.1  | Error: getaddrinfo ENOTFOUND
23:29:32 web.1  |     at errnoException (dns.js:37:11)
23:29:32 web.1  |     at Object.onanswer [as oncomplete] (dns.js:124:16)
23:29:32 web.1  | exited with code 8
23:29:32 system | sending SIGTERM to all processes
SIGTERM received

The 'error' event emitted by the web socket client was not being
handled, so no one was catching the exception, and that made the server
abort