RFR: JDK-8047810, DeviceManager throws IOException while opening port by config

[Jen Dority]

issue: https://bugs.openjdk.java.net/browse/JDK-8047810
webrev: http://cr.openjdk.java.net/~jld/8047810/

Hi All,

Need a review for an issue keeping GPIOPort APIs from working properly. 
Traced the issue to bad return value checking (looking for 
JAVACALL_DIO_FAIL instead of JAVACALL_FAIL) and made some additional 
cleanup to issues I found along the way.

Thanks,
Jen