Revert "xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel"

This reverts commit ddacf5ef.
As when booting the kernel under Amazon EC2 as an HVM guest it ends up
hanging during startup. Reverting this we loose the fix for kexec
booting to the crash kernels.

Fixes Canonical BZ #901305 (http://bugs.launchpad.net/bugs/901305

)

Tested-by: Alessandro Salvatori <sandr8@gmail.com>
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>