cert.pem 400 after updating stable 5.7

[Tim Kuijsten]

Every time I update my 5.7 systems by following stable the permissions 
of /etc/ssl/cert.pem are set to 400. Noticed this because OpenSMTPD 
stopped sending mail since it can not verify ssl connections: TempFail, 
"stat=Network error on destination MXs".

Cheers,
-Tim