guest-overlay: remove password hash

Remove the embedded password hash from the guest-overlay role. Instead generate that specific hash on task execution. Doesn't change the hardcoded guest password, but makes the same information more readable.

guest-overlay/tasks/main.yml

@@ -16,7 +16,7 @@
     home: "/guests/home/gast"
     group: gast
     # yamllint disable-line rule:line-length
-    password: $6$F03ruuLNpygmNPj0$fYWL/GFUowsCFxn1kH6rEG1CgdX99jTCWhDpkd4fLBWAQtEsp2PudDHUUUvNaM3MO9kfW4fONSy5ui61hwidc.
+    password: "{{ 'gast' | password_hash('sha512', 'F03ruuLNpygmNPj0') }}"
     shell: "/bin/bash"
     state: present
   tags: