Set *_temp_path location to $ServRoot/

Linux distributions build nginx with options like
`--http-client-body-temp-path=` to set default location of directories
for temporary files under /var/tmp/nginx or /var/lib/nginx.
The problem is, when running tests as part of the package build
process, these directories are not writtable. Therefore it's needed to
override location of these directories in the generated nginx.conf.

Author: jirutka

lib/Test/Nginx/Util.pm

@@ -918,6 +918,12 @@ http {
     default_type text/plain;
     keepalive_timeout  68;
 
+    client_body_temp_path "$ServRoot/client_body_temp";
+    proxy_temp_path "$ServRoot/proxy_temp";
+    fastcgi_temp_path "$ServRoot/fastcgi_temp";
+    scgi_temp_path "$ServRoot/scgi_temp";
+    uwsgi_temp_path "$ServRoot/uwsgi_temp";
+
 $http_config
 
     server {