phosphor: net-snmp: move to recipes-protocols

No functional change, but move net-snmp from recipes-connectivity to
recipes-protocols to match the hierarchy of the meta-networking layer.

(From meta-phosphor rev: a7223f270e7a18a8e486b229c8f1b08ef0609c9c)

Change-Id: Ifeda4c7543f4102c7b85086c27f8fbdba1e91314
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>