Merge pull request #334 from gfgtdf/wesnothd_sides

allow every client to ask for random seed.

assume this scenaio:

[scenario]
## human sides 1,2
  [event]
    name = prestart
    [message]
      speaker = narrator
      message = "Hello"
    [/message]
    {GENERIC_UNIT .....}
  [/event]
[/scenario]

previously, in this scenario client 2 would have to wait for side 1 to click away the [message] because of the random seed required by {GENERIC_UNIT ..} because only client 1 was allowed to ask the server for a random seed (Note that waiting during prestart event means black screen), this patch is intended to fix such situations.
simplyfy mpsync

That huge block in pull_remote_choice existed becasue we don't want to
return becasue we dont wan't to make choices for sides that we only
controll  temporary.
With the 'new' idle controller type this can be simplyfied by just not
making choices for idle sides.
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simplyfy mpsync

this is not needed anymore
simplyfy :controller logic