RFR [13] 8224730: java.net.ServerSocket::toString not invoking checkConnect

[Chris Hegarty]

Please review this small change to ServerSocket::toString so that it
correctly implements its specified behaviour ( to reveal the local
address if SecurityManager::checkConnect succeeds ). Looks like this was
a minor oversight in the implementation that was not caught by testing,
as there was no fine grained test for it. This review contains a
comprehensive test.

Additionally, the ServerSocket::toString specification would benefit
from a minor clarification that checkConnect is only invoked when the
socket is bound. ( A CSR will be filed for this )

https://cr.openjdk.java.net/~chegar/8224730/webrev.00/

-Chris.