Fix netbsd compiler warning:
Fix netbsd compiler warning:

In file included from /home/buildbot/bs-sctplab/netbsd/build/usrsctplib/netinet/sctp_os_userspace.h:448:0,
                 from /home/buildbot/bs-sctplab/netbsd/build/usrsctplib/netinet/sctp_os.h:74,
                 from /home/buildbot/bs-sctplab/netbsd/build/usrsctplib/user_socket.c:35:
/home/buildbot/bs-sctplab/netbsd/build/usrsctplib/user_socket.c: In function 'usrsctp_connect':
/home/buildbot/bs-sctplab/netbsd/build/usrsctplib/user_malloc.h:191:26: error: 'sa' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define FREE(addr, type) free((addr))
                          ^
/home/buildbot/bs-sctplab/netbsd/build/usrsctplib/user_socket.c:2139:19: note: 'sa' was declared here
  struct sockaddr *sa;
                   ^

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