Discrepancy in different LtpEngine::TransmissionRequest postconditions

[BrianSipos]

The different overloads/forms of LtpEngine::TransmissionRequest seem to behave differently about sending segments after starting a new outgoing transfer session. The function TrySendPacketIfAvailable() is called for the forms that take a parameter of transmission_request_t but is not called for the other (bare session parameters) forms.

A workaround is to always use the transmission_request_t forms, but it seems like this is a bug if the other overloads don't work consistently.