Fix calculation of days until API key expires and short the API key in the emails
API key reminder should not send the API key in clear text. Shorten displayed
key to 5 chars.
Calculation of remaining days until a API key expires was wrong as it took into
account only the days part of the date and ignored month or year.
fixes #4230
fixes #4231
Signed-off-by: Karsten Hopp <karsten@redhat.com>