compare-puppet-catalogs: fix hiera copy

After we changed the name of the hiera dir in the production hiera
config, the substitution we do here was incorrect. This fix should make
hiera work again correctly in the puppet compiler

Change-Id: I20bb35c62b099fda6c96efc2fdd9844a7137e6b8
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>