Fixed checking ngx_tcp_push() and ngx_tcp_nopush() return values.

No functional changes.

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 680b664..e6f9c09 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2020,7 +2020,7 @@
     }
 
     if (c->tcp_nopush == NGX_TCP_NOPUSH_SET) {
-        if (ngx_tcp_push(c->fd) == NGX_ERROR) {
+        if (ngx_tcp_push(c->fd) == -1) {
             ngx_log_error(NGX_LOG_CRIT, c->log, ngx_socket_errno,
                           ngx_tcp_push_n " failed");
             ngx_http_upstream_finalize_request(r, u,

src/os/unix/ngx_freebsd_sendfile_chain.c

diff --git a/src/os/unix/ngx_freebsd_sendfile_chain.c b/src/os/unix/ngx_freebsd_sendfile_chain.c
index 4822e72..3d415bd 100644
--- a/src/os/unix/ngx_freebsd_sendfile_chain.c
+++ b/src/os/unix/ngx_freebsd_sendfile_chain.c
@@ -135,7 +135,7 @@
             if (ngx_freebsd_use_tcp_nopush
                 && c->tcp_nopush == NGX_TCP_NOPUSH_UNSET)
             {
-                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
+                if (ngx_tcp_nopush(c->fd) == -1) {
                     err = ngx_socket_errno;
 
                     /*

src/os/unix/ngx_linux_sendfile_chain.c

diff --git a/src/os/unix/ngx_linux_sendfile_chain.c b/src/os/unix/ngx_linux_sendfile_chain.c
index b44724c..5695839 100644
--- a/src/os/unix/ngx_linux_sendfile_chain.c
+++ b/src/os/unix/ngx_linux_sendfile_chain.c
@@ -130,7 +130,7 @@
 
             if (c->tcp_nodelay == NGX_TCP_NODELAY_UNSET) {
 
-                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
+                if (ngx_tcp_nopush(c->fd) == -1) {
                     err = ngx_socket_errno;
 
                     /*