librenms requires snmp

Librenms requires the snmp package to work. Seems like it calls
snmpget/snmpwalk and the rest of the family. This had been commented out
in I6620ff7bb206d8fee4fb18607930195382611ec9 since base::puppet also
included it and ended up in a duplicate definition. Since that part is
no longer true, uncomment the snmp package in librenms

Change-Id: I8c067162b1ff4be6bbbed83ae6c7688896ce39e8
Merge "librenms requires snmp" into production