CA-120445: include fbcon in kernel
CA-122087: xen-netback: stop the VIF thread before unbinding IRQs

If the VIF thread is still running after unbinding the Tx and Rx IRQs
in xenvif_disconnect(), the thread may attempt to raise an event which
will BUG (as the irq is unbound).
CP-4805: Call kexec before offlining non-crashing CPUs