don't explode if domain doesn't already exist in build_kvm.sh
diff --git a/tools/build_kvm.sh b/tools/build_kvm.sh
index cc63ba2..38a4943 100755
--- a/tools/build_kvm.sh
+++ b/tools/build_kvm.sh
@@ -58,7 +58,7 @@
 VM_IMAGE=$IMAGES_DIR/$DIST_NAME.$GUEST_NAME.raw
 
 # Mop up after previous runs
-virsh destroy $GUEST_NAME
+virsh destroy $GUEST_NAME || true
 
 # Where this vm is stored
 VM_DIR=$KVMSTACK_DIR/instances/$GUEST_NAME