client/Inode.cc: prefer prefix ++operator for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
cls/rgw/cls_rgw.cc: prefer prefix --operator for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
client/hadoop/CephFSInterface.cc: prefer prefix ++operator for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>