[SNMP4J] possible concurrent modification exception in UsmUserTable?

[Aaron Loyd]

The UsmUserTable class uses the not thread safe TreeMap.  It seems that if one
thread were to do snmp.getUSM().addUser() while another thread were doing
getUser() the iterator would throw a ConcurrentModificationException.

We see that if we run two or more threads to do SNMPv3 queries, sometimes one or
more of the queries will simply time out and not return any data but sometimes
succeed.