Use existing keychain entry for upload

[samdeane]

Instead of looking for "AC_PASSWORD" in the keychain, look for an existing web form entry which should get set when logging in via Safari.

The format should be:

name: idmsa.apple.com (example@elegantchaos.com)
kind: Web form password
account: example@elegantchaos.com
where: https://idmsa.apple.com