RFR: JDK-8202105: jshell tool: on exiting, terminal echo is disabled

[Jan Lahoda]

Hi,

Under:
https://bugs.openjdk.java.net/browse/JDK-8194750

j.i.Console was changed to capture the state of the terminal echo at 
creation time, and to restore it on shutdown.

That is problematic at least in jshell, where the terminal is already in 
the raw mode when j.i.Console is created, and so "echo disabled" is 
recorded there. So even though jshell itself sets the terminal into the 
original mode when it terminates, the shutdown hook in j.i.Console, 
which is run later, sets the echo to off even if it was enabled before 
the VM started.

My understanding is that the shutdown hook is only needed in case the VM 
goes down while readPassword is running. So I tried to change the 
shutdown hook to only work while readPassword is running.

Bug: https://bugs.openjdk.java.net/browse/JDK-8202105
Webrev: http://cr.openjdk.java.net/~jlahoda/8202105/webrev.00/

What do you think?

Thanks,
     Jan