#292 tau_getTrnVehCnt( ) not working if OpTrnDir is not already valid

[Anders Öberg]

The function tau_getTrnVehCnt( ) requires the opTrnDir. The check in the function only requests the TrnDir not the OpTrnDir. If no other function request the opTrnDir this function will never return NO_ERR.

The check in the function shall be similar to what is done in tau_getOpTrDirectory( ) or even better call tau_getOpTrDirectory( ) from tau_getTrnVehCnt( ).