Correlation Ids are wrongly set on outgoing commands

[rhinof]

When a saga sends a command grabbit wrongly sets the saga correlation id on the outgoing saga.

Expected result: a command being sent by a saga via invocation.Bus().Send(...) should not contain a value in the SagaCorrelationID header.

Actual: the SagaCorrelationID header is set with the value of the SagaID