DB2 requires columns which are part of primary keys to be non-nullable.
Animal.hbm.xml in the TS, used by ASTParserLoadingTest, defines a User_permissions table without specifying the NOT NULL constraint on the userId column. The resulting SQL:

create table "User_permissions" (
            userId bigint,
            permissionId integer not null,
            permissionName varchar(255),
            primary key (userId, permissionId)
        )

which makes the test hang forever during cleanup after the test.

This can be probably fixed by upgrade to Hibernate 5.0.2 - specifically this commit fixes it:
https://github.com/hibernate/hibernate-orm/commit/1ae495b7c96219c47917f37903459e8fbb18a804
which will make Hibernate add a NOT NULL constraint automatically for columns which are components of primary keys.