TxImporter is not thread-safe and it is used in concurrent environment

com.arjuna.ats.internal.jta.transaction.arjunacore.jca.TxImporter is used by com.arjuna.ats.internal.jta.transaction.arjunacore.jca.XATerminatorImple. The field TxImporter._transactions is static and there can be more XATerminatorImple objects in JVM or there can more threads in one XATerminatorImple object. The access to that field is not synchronized. Type of the field is non-synchronized HashMap.