system-source: Demote the json-parser() warning to a debug message

Not having the json module installed by default is fairly common, @cim
messages on the other hand, are not. To make startup less annoying for a
large number of users, demote the warning about json-parser() missing to
a debug message.

This addresses one part of #329.

Reported-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
hostname: Demote the FQDN warning to a verbose message

On a lot of desktop machines (and in private networks), the hostname
will not be fully qualified, so the warning is just noise. Demote it to
a message only displayed in verbose mode.

This fixes the other half of #329.

Reported-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #330 from algernon/h/3.6/annoying-startup-messages

Silence two annoying startup messages