fix #4531: acme plugins: correct change detection of dirty form fields

Fix the ACME plugin edit form only detecting dirtychanges once the
value of a textfield was dirtied and then changed back to the
original.

This behaviour is caused as we cannot reuse the field's
resetOriginalValue method, due to that cause breakage here, e.g., if
the value was edited, then another plugin (without a schema) gets
selected, and then one would switch back again to the previous plugin,
it would cause the (actually still dirty) value to get registered as
new original one by mistake.

So the fix here is to keep the manual originalValue tracking, but add
the missing call to checkDirty after setting the originalValue to
refresh the dirty flag.

Fixes: 45708891 ("ui: add ACMEPluginEdit window") from pve-manager
Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
 [TL: record reason for originalValue handling & sligthly reword ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/window/ACMEPluginEdit.js

@@ -127,6 +127,7 @@ Ext.define('Proxmox.window.ACMEPluginEdit', {
 		    if (me.createdFields[key]) {
 			me.createdFields[key].setValue(value);
 			me.createdFields[key].originalValue = me.originalValues[key];
+			me.createdFields[key].checkDirty();
 		    } else {
 			extradata.push(`${key}=${value}`);
 		    }