The value of vRtrPimNgMvpnUMHPEStandbyAddr specifies the
value of the address assigned to a standby PE to be used in UMH
selection for MVPN source redundancy. This value cannot be modified
without shutting down the MVPN instance.
An address instance of 'vRtrPimNgMvpnUMHPEStandbyAddr' can be
associated with only a single address instance of
'vRtrPimNgMvpnUMHPEAddr' or in other words the pairing must be
unique.
This object MUST be specified at row creation time.