[SNMP] - Require net-snmp-utils

Previously, we only required net-snmp, but net-snmp-utils provides
snmpusm, which is used to change authentication. Require it.

Change-Id: I3d72b92832dbc8f352bbb55db6ca52a7eaaa4056
Signed-off-by: Ryan Barry <rbarry@redhat.com>