visdiff: Add timeout & logging to troubleshoot hang
visdiff: Add timeout & logging to troubleshoot hang

Not sure why visdiff is hanging sometimes, but it would be useful to
gain some context the next time it occurrs.

keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client