Remove amanda from carbon

Remove backup::client (amanda) from carbon. The current manifest has
been broken for a long time, as amanda gets installed and uninstalled
during the same puppet run, on every puppet cycle. This happens because
amanda-client pulls openbsd-inetd, which install-server explicitly
purges.

As it has been obviously broken for a while and our amanda installation
is on its way to the graveyard, remove amanda from carbon altogether.

Change-Id: I2060b6bd655d4ba00fd92bf7cf4c954b8e0f1476