Revert "src: call uv_loop_delete() on exit in debug mode"

Don't call uv_loop_delete() until we've figured out a way to gracefully
close open handles.  See also commit 4915884 and its subsequent revert
in commit 980cbd5.

This reverts commit 556b890ad9.

src/node.cc

@@ -3179,7 +3179,6 @@ int Start(int argc, char *argv[]) {
 #ifndef NDEBUG
   // Clean up. Not strictly necessary.
   V8::Dispose();
-  uv_loop_delete(uv_default_loop());
 #endif  // NDEBUG
 
   // Clean up the copy: