osmium: remove specific classes.

Since osmium has been a sandbox/playground and puppet ends up being
disabled or failing, which makes it problematic for production
sometimes, we remove all the specific classes and re-enable puppet on it.

Change-Id: I86f42a2050fbbd02f5754e2eba6baf877ec4c78e
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>