Allows dropping the xmlsec1-ecdsa-assert.patch.1 backport.

Also fix the generated test certs + generator script to avoid expired
certs for a while (.db files generated with Firefox 57.0).

Change-Id: I8cba9a01633a3952c845e15e23b18d44544cdb59
Reviewed-on: https://gerrit.libreoffice.org/56123
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>