fix: allow ssh login for nova user in nova-ssh image (#1246)

nologin avoids ssh connection between noova-computes which is required for live migrations.
fix #1245

Reviewed-by: Mohammed Naser <mnaser@vexxhost.com>
diff --git a/zuul.d/container-images/nova-ssh.yaml b/zuul.d/container-images/nova-ssh.yaml
index 3650306..df638aa 100644
--- a/zuul.d/container-images/nova-ssh.yaml
+++ b/zuul.d/container-images/nova-ssh.yaml
@@ -46,6 +46,7 @@
           build_args:
             - "RELEASE={{ zuul.branch | replace('stable/', '') }}"
             - PROJECT=nova
+            - SHELL=/bin/bash
           tags:
             - "{{ zuul.branch | replace('stable/', '') }}"
     files: &container_image_files