INT-3252 Fix AlternativeJdkIdGenerator

JIRA: https://jira.springsource.org/browse/INT-3252

Remove the use of `SecureRandom.generateSeed()` which is not
supported on some platforms.

Note: While this change does not reflect the custom IBM
code noted in the JIRA issue, it does revert the initial
SecureRandom generation to use the same code as
UUID.randomUUID(), so the expectation is that this will
work fine on zOS.