Admin password check works with yescrypt; shorter Blancco version warning

chpasswd and passwd write yescrypt ($y$) hashes, which the openssl $6$
comparison could not read: every re-run set the pxe password again, and a
box whose password was 'pxe' in yescrypt passed the pxe_admin_password
requirement. Both Admin tasks now compare with crypt(), which handles every
scheme. The config.img warning names the two Blancco versions instead of
the staging guard's merge instructions.

webapp/services/blancco_update.py

@@ -1011,10 +1011,15 @@ def refresh_live_prefs():
                 ours = f.read()
             try:
                 new = patch_config_img(cfg, ours)
-            except (StageBlocked, ValueError) as e:
-                warning = (f"the live config.img (BIOS boot) was not updated: {e} "
+            except StageBlocked:
+                live = prefs_version(cpio_member(cfg, "preferences.xml") or b"") or "?"
+                warning = (f"the live config.img (BIOS boot) is Blancco {live}, older than our "
+                           f"{prefs_version(ours) or '?'} preferences, so it was not updated. "
                            "Stage a current release on Updates > Blancco releases.")
                 new = cfg
+            except ValueError as e:
+                warning = f"the live config.img (BIOS boot) was not updated: {e}"
+                new = cfg
             if new != cfg:
                 _atomic_write(cfg_path, new)
                 changed = True

webapp/tests/test_share_accounts.py

@@ -190,7 +190,8 @@ class ShareAccounts(Fixture):
         with open(os.path.join(BU.blancco_root(), "config.img"), "wb") as f:
             f.write(cfg)
         done = SA.set_password("blancco", PW)
-        self.assertTrue(any("WARNING" in d and "config.img" in d for d in done), done)
+        self.assertTrue(any("WARNING" in d and "config.img (BIOS boot) is Blancco 7.15" in d
+                            and "older than our 7.20" in d for d in done), done)
         with open(BP.served_prefs_path(), "rb") as f:
             self.assertEqual(self.prefs_share_pw(f.read()), PW)
         with open(os.path.join(BU.blancco_root(), "config.img"), "rb") as f: