securetransport: Add debug message for shutdown, fix error handling
securetransport: Add debug message for shutdown, fix error handling

errSSLClosedGraceful does not seem to be a valid return code
for this function.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc