Bug 1350887 - Propagate errors thrown when starting server.TCPListener; r=whimboo

Errors thrown are printed to console and there is no point in having a
custom catch to print it.

This also makes it possible to start Marionette programmatically without
worrying about disappearing errors.

MozReview-Commit-ID: GGhyCyYqJg

--HG--
extra : rebase_source : 28937d94c8688c05887dcbf7dcf862e7bdc3a6c7

testing/marionette/components/marionette.js

@@ -297,9 +297,6 @@ MarionetteComponent.prototype.init = function () {
     s = new server.TCPListener(prefs.port, prefs.forceLocal);
     s.start();
     this.logger.info(`Listening on port ${s.port}`);
-  } catch (e) {
-    this.logger.error(`Error on starting server: ${e}`);
-    dump(`${e.toString()}\n${e.stack}\n`);
   } finally {
     if (s) {
       this.server = s;