altool isn't guaranteed to clean up after itself, e.g. if an earthquake
takes down the Developer ID Notary Service (thanks to Jim Young for
tracking this down). Instead of checking for the existence of tokens,
check their existence and age.
Change-Id: Iac216d524a4894115ecf33589af1bbdebcc9cbab
Reviewed-on: https://code.wireshark.org/review/33856
Reviewed-by: Gerald Combs <gerald@wireshark.org>