Coordinate usdDnsServerListIndex value allocation for entries in
usdDnsServerListTable.
A GET of this object returns the next available index value to be used
to create an entry in the associated table; or zero, if no valid index
value is available. This object also returns a value of zero when it is
the lexicographic successor of a varbind presented in an SNMP GETNEXT or
GETBULK request, for which circumstance it is assumed that index
allocation is unintended.
Successive GETs will typically return different values, thus avoiding
collisions among cooperating management clients seeking to create table
entries simultaneously.