librenms: make custom function compatible with puppet 3

Under puppet 3, all arguments of a function must be explicitly passed as
an anonymous array, even if they have just one element.

Change-Id: I21403f6e4546c0be294b4ee5a795d6f6ddbc059b
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>
Adding manybubbles on analytics1004 for some elasticsearch testing

Change-Id: I012889cccef0f3ba73fa377701afad29cc44082a