The password a user must supply to use the service.
Corresponds directly to SERVICE PASSWORD and the
presence of the label 'Password' following the label
'Enabled Characteristics:' in the SERVICE
CHARACTERISTICS display.
When setting this value, the management system must
supply eight octets, filling with zeros from the
first octet. That is, the value '1ab42' would be
expressed as '0.0.0.0.0.1.ab.42'. Setting the value
to zero disables the password check.
When returning this value, the agent always returns
a zero length OCTET STRING.