nfs-server: update shell module usage

nfs-server/tasks/main.yml

@@ -78,7 +78,11 @@
   when: nfs_krb is defined
 
 - name: check that we have a valid service principal
-  shell: klist -k /etc/krb5.keytab | grep "nfs/{{ ansible_fqdn }}"
+  shell: |
+    set -o pipefail
+    klist -k /etc/krb5.keytab | grep "nfs/{{ ansible_fqdn }}"
+  args:
+    executable: /bin/bash
   register: principal
   failed_when: false
   tags: