When using cached file descriptors, differences betweenthe sysfs filesystem and normal filesytems show up.In particular, extraneous data are not persisted betweenindividual write calls (in sysfs, they're handed to thekernel driver; reads are again handled by a kernel driver).This commit repairs the illusion by opening and closingthe file for each read/write separately.# Conflicts:#src/test/java/fake_ev3dev/ev3dev/utils/io/SysfsFile.java