polkit fix (with centos package)

Rather than just removing the sticky bit on pkexec

packer/azurehpc-lustre-2.12.5.json

@@ -27,7 +27,7 @@
             ],
             "execute_command": "chmod +x {{ .Path }}; {{ .Vars }} sudo -E sh '{{ .Path }}'",
             "inline": [
-                "chmod 0755 /usr/bin/pkexec",
+                "yum -y install polkit",
                 "chmod +x /tmp/lustre-setup-scripts/*.sh",
                 "/tmp/lustre-setup-scripts/disable-selinux.sh",
                 "/tmp/lustre-setup-scripts/additional-pkgs.sh",