Fix issues after re-exec

 - @bot.channels was not filled after a re-exec
 - Write the NAMES command directly to the socket. If it is queued (as
   it was), other messages may be processed too early which may cause a
   dead-lock.
 - The list of joined channels are saved before re-exec, and used
   afterwards, instead of using the config. This is because the config
   may have changed, so joined channels are no longer in the config.
 - The IRC mask of the bot is saved before re-exec, and used afterwards.
   This is done instead of using @bot.mask, as that is not ready at that
   point.
Merge remote-tracking branch 'trygve/re-exec'