Core: silenced getsockopt(TCP_FASTOPEN) messages on FreeBSD.

FreeBSD returns EINVAL when getsockopt(TCP_FASTOPEN) is called on a unix
domain socket, resulting in "getsockopt(TCP_FASTOPEN) ... failed" messages
during binary upgrade when unix domain listen sockets are present in
the configuration.  Added EINVAL to the list of ignored error codes.

src/core/ngx_connection.c

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 9a74758..878c6be 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -305,7 +305,9 @@
         {
             err = ngx_socket_errno;
 
-            if (err != NGX_EOPNOTSUPP && err != NGX_ENOPROTOOPT) {
+            if (err != NGX_EOPNOTSUPP && err != NGX_ENOPROTOOPT
+                && err != NGX_EINVAL)
+            {
                 ngx_log_error(NGX_LOG_NOTICE, cycle->log, err,
                               "getsockopt(TCP_FASTOPEN) %V failed, ignored",
                               &ls[i].addr_text);