RFR: JDK-8073057 JDK-8073058

[alexey karaksin]

issues:
https://bugs.openjdk.java.net/browse/JDK-8073058 DNF for pin that was 
exported previously
https://bugs.openjdk.java.net/browse/JDK-8073057 Add wait procedure 
after GPIO export

webrev: http://cr.openjdk.java.net/~amironov/8073057/

1. In the GPIO Pin open procedure added check if file 
/sys/class/gpio/gpioN/direction exists, if so, no necessary write pinn 
number to the export file.
2. added usleeps between attempts to open write to the export file and 
open /sys/class/gpio/gpioN/direction. usleep is because neither 
"inotify" nor fanotify handle sysfs gpioN directory creation properly.