BUG: TimeoutManager seems to reset TimeSent header

[ramonsmits]

The TimeSent header seems to be overwritten with the time the timeout manager dispatched the message to the transport which results in the real timesent value to be lost.

This results in aged timeout manager entries that can be many years old to be sent as now.

Tested with:
Core:

    <PackageReference Include="NServiceBus.RabbitMQ">
      <Version>4.2.1</Version>
    </PackageReference>
    <PackageReference Include="NServiceBus.RavenDB">
      <Version>4.2.6</Version>
    </PackageReference>
    <PackageReference Include="RavenDB.Client">
      <Version>3.5.9</Version>
    </PackageReference>

This configuration cannot be tested with a later version due to the timeout manager not being used.

With v7 only MSMQ would currently be affected but with v6 most transports can be affected due to timeout manager its backwards compatibility.

Data

RavenDB Timeout document:

{
    "Destination": "RavenToSqlPersistence",
    "SagaId": "00000000-0000-0000-0000-000000000000",
    "State": "PD94bWwgdmVyc2lvbj0iMS4wIj8+PE15TWVzc2FnZSB4bWxuczp4c2k9Imh0dHA6Ly93d3cudzMub3JnLzIwMDEvWE1MU2NoZW1hLWluc3RhbmNlIiB4bWxuczp4c2Q9Imh0dHA6Ly93d3cudzMub3JnLzIwMDEvWE1MU2NoZW1hIiB4bWxucz0iaHR0cDovL3RlbXB1cmkubmV0LyI+PEF0PjIwMjAtMDItMTdUMTc6MTU6NDkuNDg3OTA2OFo8L0F0PjwvTXlNZXNzYWdlPg==",
    "Time": "2020-02-17T17:17:19.4879060Z",
    "OwningTimeoutManager": "RavenToSqlPersistence",
    "Headers": {
        "NServiceBus.MessageId": "964377a2-8493-460e-84c5-ab64011c7f75",
        "NServiceBus.MessageIntent": "Send",
        "NServiceBus.CorrelationId": "964377a2-8493-460e-84c5-ab64011c7f75",
        "NServiceBus.OriginatingMachine": "ZOLDER",
        "NServiceBus.OriginatingEndpoint": "RavenToSqlPersistence",
        "$.diagnostics.originating.hostid": "34b86c359d09498213e5d5f2b16a714e",
        "NServiceBus.ReplyToAddress": "RavenToSqlPersistence",
        "NServiceBus.ContentType": "text/xml",
        "NServiceBus.EnclosedMessageTypes": "MyMessage, Seeder, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null",
        "NServiceBus.ConversationId": "0640d678-77e3-4f78-8265-ab64011c7f85",
        "NServiceBus.Version": "6.5.9",
        "NServiceBus.TimeSent": "2020-02-17 17:15:49:568909 Z",
        "NServiceBus.Timeout.RouteExpiredTimeoutTo": "RavenToSqlPersistence",
        "NServiceBus.Timeout.Expire": "2020-02-17 17:17:19:487906 Z",
        "NServiceBus.Transport.RabbitMQ.ConfirmationId": "1",
        "NServiceBus.NonDurableMessage": "False"
    }
}

Headers of received timeout:

NServiceBus.MessageId 964377a2-8493-460e-84c5-ab64011c7f75
NServiceBus.MessageIntent Send
NServiceBus.CorrelationId 964377a2-8493-460e-84c5-ab64011c7f75
NServiceBus.OriginatingMachine ZOLDER
NServiceBus.OriginatingEndpoint RavenToSqlPersistence
$.diagnostics.originating.hostid 34b86c359d09498213e5d5f2b16a714e
NServiceBus.ReplyToAddress RavenToSqlPersistence
NServiceBus.ContentType text/xml
NServiceBus.EnclosedMessageTypes MyMessage, Seeder, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
NServiceBus.ConversationId 0640d678-77e3-4f78-8265-ab64011c7f85
NServiceBus.Version 6.5.9
NServiceBus.TimeSent 2020-02-17 17:17:20:152072 Z
NServiceBus.Timeout.RouteExpiredTimeoutTo RavenToSqlPersistence
NServiceBus.Timeout.Expire 2020-02-17 17:17:19:487906 Z
NServiceBus.Transport.RabbitMQ.ConfirmationId 3
NServiceBus.NonDurableMessage False
NServiceBus.RelatedToTimeoutId