Reset channel info on server disconnect

[vanosg]

Found by: renols
Patch by: Geo
Fixes: #203

One-line summary:
Update channel info on server disconnect

Additional description (if needed):
Previous fix addressed channel parts/kicks, but missed separate code thread of dealing with server disconnects, such as when utilized via .jump. This exports reset_chan_info() to the server mod and calls when using from nuke_server().

Thanks to @rco133 for his continued persistence on this bug!

Test cases demonstrating functionality (if applicable):

.tcl botonchan #geo
Tcl: 1
.jump
[18:52:21] #Geo# jump
Jumping servers......
[18:52:21] Trying server [foo.com]:+7000
[18:52:21] Failed connect to foo.com (Operation now in progress)
.tcl botonchan #geo
Tcl: 0
....
....
[19:02:20] myBot joined #geo
.tcl botonchan #geo
Tcl: 1