MINOR: deinit: fix memory leak

deinit() did not free the conf.file member of server objects.
diff --git a/src/haproxy.c b/src/haproxy.c
index 74b2687..13c3d26 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1175,6 +1175,7 @@
 			free(s->check.bo);
 			free(s->agent.bi);
 			free(s->agent.bo);
+			free((char*)s->conf.file);
 			free(s);
 			s = s_next;
 		}/* end while(s) */