qemu: allow creation of a paused domain

qemu: allow creation of a paused domain

https://bugzilla.redhat.com/show_bug.cgi?id=589465

Some guests (eg with badly configured grub, or Windows' installation cd)
require quick response from the console user. That's why we have a
"launchPaused" option in vdsm.

To implement it via libvirt, we need to ask libvirt not to call
qemuMonitorStartCPUs() after starting qemu.  Calling virDomainStop
immediately after the domain is up is inherently raceful.

* src/qemu/qemu_driver.c (qemudStartVMDaemon): Add new parameter;
all callers adjusted.
(qemudDomainCreate): Implement support for new flag.