Add debian-stretch nodeset

And make this the default nodeset by setting it on the base job.

Change-Id: Ifbe939f7e81fab75b68b2507595b482c8ef71a85

zuul.d/jobs.yaml

diff --git a/zuul.d/jobs.yaml b/zuul.d/jobs.yaml
index d2bb940..87e0311 100644
--- a/zuul.d/jobs.yaml
+++ b/zuul.d/jobs.yaml
@@ -56,7 +56,7 @@
       - zuul: opendev.org/zuul/zuul-jobs
     timeout: 1800
     post-timeout: 1800
-    nodeset: debian-testing
+    nodeset: debian-stretch
 
 # See the procedure described above "base" before making changes to
 # this job.
@@ -75,4 +75,4 @@
       - zuul: opendev.org/zuul/zuul-jobs
     timeout: 1800
     post-timeout: 1800
-    nodeset: debian-testing
+    nodeset: debian-stretch

zuul.d/nodesets.yaml

diff --git a/zuul.d/nodesets.yaml b/zuul.d/nodesets.yaml
index 28e0ff6..0e11d14 100644
--- a/zuul.d/nodesets.yaml
+++ b/zuul.d/nodesets.yaml
@@ -1,6 +1,5 @@
 - nodeset:
-    name: debian-testing
+    name: debian-stretch
     nodes:
-      - name: debian-testing
-        label: testlabel
-# TODO: use a real label
+      - name: testnode
+        label: debian-stretch-8G