This avoids us trying to restore the original resolution when we're fullscreen
and an X error happens. As restoring fullscreen is a bad idea then as this
involves making more X calls, which can get us stuck (in side an XLockDisplay
call for example).

When starting spicec with --controller, SPICE_XPI_SOCKET environment
variable must be defined so spicec and the controller can be connected.

uses VSC_Error with code==VSC_SUCCESS instead. This means that the VSC_Error
message is overloaded. Instead of the other option of adding a message id,
since the connection is TCP so no messages may be dropped or reordered, by
having each message followed by a response there is no ambiguity. Still
this commit adds a queue for messages that we only have one of which outstanding
at a time, i.e. send, wait for response, send the next, etc. This further
simplifies the logic, while not adding much overhead since only when spicec
starts up it has a situation where it needs to send two events (ReaderAdd
and ATR for Card Insert).

This patch stops us from drawing the spice client watermark at the top of
the virtual machine view. We have had requests through several channels to
remove this as it has little added value, and is seen as annoying by some.
Given that we now also have a bugzilla for this I think it is time we really
remove it.
(cherry picked from commit 392ed65dda1a28c85f04ebb09924c6ce83dbdf2b)

For not too old spice-migration, minor is 1.
For older (ancient) spice-migration, minor is 0.

Affects only VM migration while a spice client is connected.