The string defined by user to fill in the
remote ID in the user-defined mode.
If the value of hh3cDhcpRelay2IfOpt82RIDMode is NOT
'userDefine', it is set to a zero-length string automatically.
Otherwise it must be set with a non-zero length string.
The SET operation of this object must be with the SET
operation of hh3cDhcpRelay2IfOpt82RIDMode.