(PDB-886) Drop [jetty] certificate-whitelist handling

Fully retire the accommodations for a (vestigial) certificate-whitelist
option in the [jetty] section.  The only valid location for that option
should now be [puppetdb].
Merge pull request #1181 from rbrw/ticket/master/pdb-886-retire-certificate-whitelist-from-jetty

(PDB-886) Drop [jetty] certificate-whitelist handling