Update nodepool-integration for Zuul v3

Zuul v3 native jobs do not setup $WORKSPACE anymore, use
$HOME/logs now.

Change-Id: I2e304513cc253bcb4f8e56b16bbca97b44e4f5ba
Needed-By: https://review.openstack.org/#/c/540595/
diff --git a/tools/nodepool-integration-setup.sh b/tools/nodepool-integration-setup.sh
index c02a016..58c39cf 100755
--- a/tools/nodepool-integration-setup.sh
+++ b/tools/nodepool-integration-setup.sh
@@ -3,7 +3,7 @@
 /usr/zuul-env/bin/zuul-cloner --workspace /tmp --cache-dir /opt/git \
     git://git.openstack.org openstack-infra/nodepool
 
-ln -s /tmp/nodepool/log $WORKSPACE/logs
+ln -s /tmp/nodepool/log $HOME/logs
 
 cd /tmp/openstack-infra/nodepool
 /usr/local/jenkins/slave_scripts/install-distro-packages.sh