stack/monitor: repair check-monitor-password-promise

This fixes a username/password confusion from c536eb7c (stack/monitor:
change frontend url promise to use username/password, 2021-07-26)

stack/monitor/buildout.hash.cfg

@@ -14,7 +14,7 @@
 # not need these here).
 [monitor2-template]
 filename = instance-monitor.cfg.jinja2.in
-md5sum = fce342a392141f91c2e1a7b40efa9896
+md5sum = b6d264a414fcf286d36f26732e971ca4
 
 [monitor-httpd-conf]
 _update_hash_filename_ = templates/monitor-httpd.conf.in

stack/monitor/instance-monitor.cfg.jinja2.in

@@ -364,7 +364,7 @@ name = check-monitor-frontend-password.py
 url = ${monitor-frontend:connection-secure_access}
 config-url = ${:url}
 config-username = ${monitor-instance-parameter:username}
-config-password = ${monitor-instance-parameter:username}
+config-password = ${monitor-instance-parameter:password}
 
 # Requests to the frontend URL should fail when no credentials are
 # supplied.