shasum -> sha256sum, .sha -> .sha256

Change-Id: I086af075a82eec9a08cf00f6397671c33746b57f
diff --git a/jobs.yaml b/jobs.yaml
index 051236a..ba6b3c0 100644
--- a/jobs.yaml
+++ b/jobs.yaml
@@ -70,7 +70,7 @@
     builders:
       - shell: stdbuf -oL -eL mispipe "sudo ~mininet/mininet/util/vm/build.py -v --branch {branch} --test sanity {flavor} --chown `whoami`"  "tr '\r' ' '"
       - shell: zip `basename -s .ovf */*.ovf`.zip */*.vmdk */*.ovf
-      - shell: shasum */*.vmdk */*.ovf *.zip > `basename -s .ovf */*.ovf`.sha
+      - shell: sha256sum */*.vmdk */*.ovf *.zip > `basename -s .ovf */*.ovf`.sha256
     publishers:
       - archive:
             artifacts: '**'