Jenkins 1.598

1. When taking slave offline by user - you can specify a reason.
If the slave is getting disconnected (i.e. after a reboot), the reason is changed to a java exception, and you can't see the original reason.

2. When a slave is in a "connecting" state (slave agent being lunched) and is in offline state - the reason doesn't appear on the computer page (/computer/host...).