[libmultipath] fix uninitialized var in discovery.c:get_serial()
[libmultipath] fix uninitialized var in discovery.c:get_serial()

grzn/multipath-tools-explained,grzn/multipath-tools-explained,unakatsuo/multipath-tools,unakatsuo/multipath-tools,unakatsuo/multipath-tools,vijaychauhan/multipath-tools,vijaychauhan/multipath-tools,gebi/multipath-tools