tool: restore excidently removed 'private static final'

I removed it by mistake[1].

[1] http://gerrit.ovirt.org/#/c/33441/1..2/backend/manager/tools/src/main/java/org/ovirt/engine/core/notifier/transport/snmp/Snmp.java,cm

Change-Id: Ic51771917e5e8ec22042f2ee6ebdc67af10e2f01
Signed-off-by: Mooli Tayer <mtayer@redhat.com>