JSSE: correct SSLSocket exception types, fix for setting fd

[cconlon]

A previous PR (#222) had introduced an internal helper method (checkAndInitSSLSocket()) to help make sure the SSLSocket was initialized and native file descriptor set. This PR makes two small fixes:

• Corrects the expected exception thrown from getInputStream() and getOutputStream() from IOException to SocketException.
• Adds an independent flag indicating if the native fd has been set or not. This allows code to initialize the cert/key, and later come back and set the file descriptor once the socket is connected.

This PR fixes our nightly Jenkins SunJSSE test.