notifier: add support for snmpv6 in SNMP_MANAGERS.

Change-Id: I9a21038928b7e553feefb9ab7669eac588c1c93c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1073498
Signed-off-by: Mooli Tayer <mtayer@redhat.com>