[XEND] Wait sufficient time for memory to balloon out before creating a new domain.

[XEND] Wait sufficient time for memory to balloon out before creating a new domain.

On the ES7000 when Dom0 boots up with all of system memory and you try
to bring up a DomU with more than 2GB of memory, xend times out before
the memory is freed causing the domain not to be created. This patch
increases the timeout depending on the amount of memory that needs to be
freed. It also places a cap on the sleep time so that it does not grow
without a limit. This fixes bug# 650

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=3D650

Signed-off-by: Aravindh Puthiyaparambil
<aravindh.puthiyaparambil@unisys.com>