Style: changed checks of ngx_ssl_create_connection() to != NGX_OK.

In http these checks were changed in a6d6d762c554, though mail module
was missed at that time.  Since then, the stream module was introduced
based on mail, using "== NGX_ERROR" check.

src/mail/ngx_mail_handler.c

diff --git a/src/mail/ngx_mail_handler.c b/src/mail/ngx_mail_handler.c
index 9d4ef56..f6b26ed 100644
--- a/src/mail/ngx_mail_handler.c
+++ b/src/mail/ngx_mail_handler.c
@@ -222,7 +222,7 @@
     ngx_mail_session_t        *s;
     ngx_mail_core_srv_conf_t  *cscf;
 
-    if (ngx_ssl_create_connection(ssl, c, 0) == NGX_ERROR) {
+    if (ngx_ssl_create_connection(ssl, c, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
         return;
     }

src/stream/ngx_stream_ssl_module.c

diff --git a/src/stream/ngx_stream_ssl_module.c b/src/stream/ngx_stream_ssl_module.c
index 937efea..da26a41 100644
--- a/src/stream/ngx_stream_ssl_module.c
+++ b/src/stream/ngx_stream_ssl_module.c
@@ -365,7 +365,7 @@
         return NGX_ERROR;
     }
 
-    if (ngx_ssl_create_connection(ssl, c, 0) == NGX_ERROR) {
+    if (ngx_ssl_create_connection(ssl, c, 0) != NGX_OK) {
         return NGX_ERROR;
     }