test relative nginx.conf, this is compatible with old versions
because cycle->root on this stage is not set

src/core/nginx.c

diff --git a/src/core/nginx.c b/src/core/nginx.c
index 27cb80f..579ee16 100644
--- a/src/core/nginx.c
+++ b/src/core/nginx.c
@@ -656,10 +656,6 @@
         cycle->conf_file.data = (u_char *) NGX_CONF_PATH;
     }
 
-    if (ngx_conf_full_name(cycle, &cycle->conf_file, 1) == NGX_ERROR) {
-        return NGX_ERROR;
-    }
-
     return NGX_OK;
 }