Initialize the sockaddr_in and sockaddr_in6 structures

Initialize the sockaddr_in and sockaddr_in6 structures

This fixes two scan-build false positives:

context.c:441:23: warning: The left operand of '!=' is a garbage value
                    || sin.sin_port != htons(lwres_udp_port))
                       ~~~~~~~~~~~~ ^
context.c:447:25: warning: The left operand of '!=' is a garbage value
                    || sin6.sin6_port != htons(lwres_udp_port))
                       ~~~~~~~~~~~~~~ ^
2 warnings generated.

The sin and sin6 structures are used as argument to recvfrom call and
they are properly filled by the call.