Signal end-of-stream when remote sends a CLOSE notification

GlobusGSSCredentialImpl fails when the remote initiates a proper
SSL shutdown. The patch changes the logic such that rather
than throwing a generic error, the new ClosedGSSException is
thrown. The InputStream implementation recognizes this exception
and signals end-of-stream to the caller.

(cherry picked from commit acd2d6674021e7e8146a3bdc6628504a53b867d3)
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>