XenAPI: stackrc now depends on nproc

Install it automatically in the devstack DomU

Change-Id: Ie282dd128ebc92377d85800585962bc8767483fe
diff --git a/tools/xen/prepare_guest.sh b/tools/xen/prepare_guest.sh
index 2b5e418..cd189db 100755
--- a/tools/xen/prepare_guest.sh
+++ b/tools/xen/prepare_guest.sh
@@ -74,6 +74,7 @@
 apt-get update
 apt-get install -y cracklib-runtime curl wget ssh openssh-server tcpdump ethtool
 apt-get install -y curl wget ssh openssh-server python-pip git sudo python-netaddr
+apt-get install -y coreutils
 pip install xenapi
 
 # Install XenServer guest utilities