OpenWsmanClient: replace sprintf with stringstream
OpenWsmanClient: replace sprintf with stringstream

sprintf is banned for security reasons,
so replace with stringstream that is not affected

Signed-off-by: Tomas Winkler <002a8af089113a6510dbc00453be711ac350fd80@intel.com>
Signed-off-by: Alexander Usyskin <2c2d03d7dae842f113743879f565d486184f22a3@intel.com>

vcrhonek/openwsman,Openwsman/openwsman,kkaempf/openwsman,kkaempf/openwsman,vcrhonek/openwsman,kkaempf/openwsman,kkaempf/openwsman,vcrhonek/openwsman,Openwsman/openwsman,Openwsman/openwsman,vcrhonek/openwsman,kkaempf/openwsman,kkaempf/openwsman,Openwsman/openwsman,vcrhonek/openwsman,vcrhonek/openwsman,Openwsman/openwsman,Openwsman/openwsman,Openwsman/openwsman,kkaempf/openwsman,vcrhonek/openwsman