This patch introduces a new class, placement::client, so that operators
can manage pythonN-osc-placement package.
backport note 1:
Because stable/train still uses absolute names to include puppet
classes, all usage of relative names are replaced.
backport note 2:
This change include the fix about the wrong client package name in unit
tests[1].
[1] e1fedebded
Change-Id: I76eb105ca532e427e4f48f84ccb5c15532456fda
(cherry picked from commit 0a59d6767a)
(cherry picked from commit a8a9b300f5)