bug 1194565 - Add retry to tools/import_mdn.py
bug 1194565 - Add retry to tools/import_mdn.py

Change tools/import_mdn.py to retry on network connection errors. This
makes is more robust against MDN server restarts.

mdn/browsercompat,renoirb/browsercompat,renoirb/browsercompat,jwhitlock/web-platform-compat,jwhitlock/web-platform-compat,renoirb/browsercompat,mdn/browsercompat,jwhitlock/web-platform-compat,mdn/browsercompat