Log spammed with Warning messages when running AB test

Description

Steps to reproduce:
1. Set the logging level to WARN.
2. Start an AB-test.

Expected:
No Warning messages

Actual:
Log spammed with Warning messages like:

WARN EPiServer.Marketing.Testing.Web.TestHandler: EvaluateKpis : pagehelper error - evaluating all kpis
System.InvalidOperationException: ValueFactory attempted to access the Value property of this instance.
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at EPiServer.Web.Routing.Internal.DefaultPageRouteHelper.get_PageLink()
at EPiServer.Marketing.Testing.Web.TestHandler.EvaluateKpis(Object sender, EventArgs e)
System.InvalidOperationException: ValueFactory attempted to access the Value property of this instance.
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at EPiServer.Web.Routing.Internal.DefaultPageRouteHelper.get_PageLink()
at EPiServer.Marketing.Testing.Web.TestHandler.EvaluateKpis(Object sender, EventArgs e)

Note:
It's been present for a while and quite some people having the issue and trying to troubleshoot the issue:
https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2017/5/valuefactory-attempted-to-access-the-value-property-of-this-instance/