Add winbind:online check timeout parameter

Add winbind:online check timeout parameter

This is a band-aid for the rather convoluted offline/online mess in winbind
right now. Winbind re-uses the offline functionality that is targeted at domain
client installations on laptops to not overload disfunctional DCs. It uses the
winbind cache timeout as the retry timeout after a DC reboot.

I am using a parametric options because when this mess is cleaned up, that
parameter needs to go away again.

I'd recommend to use something like

winbind:online check timeout = 30

in typical LAN environments. This means a reconnect is attempted every 30
seconds.

Volker
(This used to be commit 9920473cc165e75ee9aa5cbb9e568eb5fb67e9e6)