[perf] test/acceptance: DrainManagerTests: cleanup previous clients

...before starting to drain.

services/real-time/test/acceptance/coffee/DrainManagerTests.coffee

@@ -29,6 +29,18 @@ describe "DrainManagerTests", ->
 		}, (e, {@project_id, @user_id}) => done()
 		return null
 
+	before (done) ->
+		# cleanup to speedup reconnecting
+		@timeout(10000)
+		RealTimeClient.disconnectAllClients done
+
+	# trigger and check cleanup
+	it "should have disconnected all previous clients", (done) ->
+		RealTimeClient.getConnectedClients (error, data) ->
+			return done(error) if error
+			expect(data.length).to.equal(0)
+			done()
+
 	describe "with two clients in the project", ->
 		beforeEach (done) ->
 			async.series [
@@ -48,8 +60,6 @@ describe "DrainManagerTests", ->
 			], done
 
 		describe "starting to drain", () ->
-			# there is an internal delay of 1000ms, shift accordingly
-			@timeout(5000)
 			beforeEach (done) ->
 				async.parallel [
 					(cb) =>

services/real-time/test/acceptance/coffee/helpers/RealTimeClient.coffee

@@ -1,5 +1,6 @@
 XMLHttpRequest = require("../../libs/XMLHttpRequest").XMLHttpRequest
 io = require("socket.io-client")
+async = require("async")
 
 request = require "request"
 Settings = require "settings-sharelatex"
@@ -55,3 +56,20 @@ module.exports = Client =
 		}, (error, response, data) ->
 			callback error, data
 
+
+	disconnectClient: (client_id, callback) ->
+		request.post {
+			url: "http://localhost:3026/client/#{client_id}/disconnect"
+			auth: {
+				user: Settings.internal.realTime.user,
+				pass: Settings.internal.realTime.pass
+			}
+		}, (error, response, data) ->
+			callback error, data
+		return null
+
+	disconnectAllClients: (callback) ->
+		Client.getConnectedClients (error, clients) ->
+			async.each clients, (clientView, cb) ->
+				Client.disconnectClient clientView.client_id, cb
+			, callback