fix strncpy call to avoid ASAN violation

Ensure we're only reading to the size of the smallest buffer, since
they're both on the stack and could potentially overlap. Overlapping is
defined as ... undefined behavior. I've looked through all available
implementations of strncpy and they still only copy from the first \0
found.

We'll also never read past the end of sun_path since we _supply_
sun_path with a proper null terminator.
void conn_free(conn *c) {
    if (c) {
        assert(c != NULL);
        assert(c->sfd >= 0 && c->sfd < max_fds);

        MEMCACHED_CONN_DESTROY(c);
        conns[c->sfd] = NULL;
        if (c->hdrbuf)
            free(c->hdrbuf);
        if (c->msglist)
            free(c->msglist);
        if (c->rbuf)
            free(c->rbuf);
        if (c->wbuf)
            free(c->wbuf);
        if (c->ilist)
            free(c->ilist);
        if (c->suffixlist)
            free(c->suffixlist);
        if (c->iov)
            free(c->iov);
#ifdef TLS
        if (c->ssl_wbuf)
            c->ssl_wbuf = NULL;
#endif

        free(c);
    }
}

void conn_free(conn *c) {
    if (c) {
        assert(c != NULL);
        assert(c->sfd >= 0 && c->sfd < max_fds);

        MEMCACHED_CONN_DESTROY(c);
        conns[c->sfd] = NULL;
        if (c->hdrbuf)
            free(c->hdrbuf);
        if (c->msglist)
            free(c->msglist);
        if (c->rbuf)
            free(c->rbuf);
        if (c->wbuf)
            free(c->wbuf);
        if (c->ilist)
            free(c->ilist);
        if (c->suffixlist)
            free(c->suffixlist);
        if (c->iov)
            free(c->iov);
#ifdef TLS
        if (c->ssl_wbuf)
            c->ssl_wbuf = NULL;
#endif

        free(c);
    }
}
