driverAttributes_getDriverId does not return DriverId

I had some problems, when I was trying to publish two devices from one service and attach two drivers of the same device category to it.

Well, I figured out, that the deviceManager_attachAlgorithm function was not able to remove the already installed drivers from the manager->drivers list cause driverAttributes_getDriverId always returned CELIX_ENOMEM.

Taking a look at the code (driverAttributes_getDriverId in device_access/device_access/private/src/driver_attributes.c), I found:

[...]
char *id_prop = properties_get(properties, "DRIVER_ID")

if (id_prop) {
status = CELIX_ENOMEM;
}
[...]

which should probably be:

[...]
char *id_prop = properties_get(properties, "DRIVER_ID")

if (id_prop == NULL) {
status = CELIX_ENOMEM;
}
[...]

I would be glad if you shortly can confirm that, so I will create a patch.