tree-wide: remove redundant assignments

We already initialize the fields a few lines up to the very same values,
hence remove this.

src/basic/socket-util.c

@@ -850,8 +850,6 @@ ssize_t send_one_fd_iov_sa(
                 cmsg->cmsg_type = SCM_RIGHTS;
                 cmsg->cmsg_len = CMSG_LEN(sizeof(int));
                 memcpy(CMSG_DATA(cmsg), &fd, sizeof(int));
-
-                mh.msg_controllen = CMSG_SPACE(sizeof(int));
         }
         k = sendmsg(transport_fd, &mh, MSG_NOSIGNAL | flags);
         if (k < 0)

src/portable/portable.c

@@ -155,7 +155,6 @@ static int send_item(
         cmsg->cmsg_len = CMSG_LEN(sizeof(int));
         memcpy(CMSG_DATA(cmsg), &data_fd, sizeof(int));
 
-        mh.msg_controllen = CMSG_SPACE(sizeof(int));
         iovec = IOVEC_MAKE_STRING(name);
 
         if (sendmsg(socket_fd, &mh, MSG_NOSIGNAL) < 0)