Fix unit test failures due to ports already in use

3 changes:

* avoid using ephemeral ports when allocating ports for listeners since
they may be immediately used as the local port in subsequent uses of
client tools. For example, in the following test code there is a risk
that dsconfig will re-use the replicationServerPort as its local port:

    // Allocate random port and release it
    replicationServerPort = TestCaseUtils.findFreePort();

    // configure replication server to listen on replicationServerPort
    TestCaseUtils.dsconfig(...);

* during server startup ensure that the LDAP, LDAPS, JMX, and admin
ports are unique

* avoid starting the server during TestNG initialization by moving
the startServer() call in the monitor test case constructor to
a @BeforeClass method.