views: Add placeholder for mac field

Add a placeholder that shows the user an example of what a valid mac
address looks like.

By now, mac needs to be specified as AABBCCDDEEFF without : for historical
reasons.

ogcp/views.py

@@ -896,6 +896,7 @@ def action_client_update():
         r = server.get('/client/info', payload)
         db_client = r.json()
 
+        form.mac.render_kw = {'placeholder': 'aabbccddeeaa'}
         form.server.data = "{0}:{1}".format(server.ip, server.port)
         form.ip.data = db_client['ip']
         form.ip.render_kw = {'readonly': True}
@@ -963,6 +964,7 @@ def action_client_add():
         r = server.get('/mode')
         available_modes = [(mode, mode) for mode in r.json()['modes']]
         form.boot.choices = list(available_modes)
+        form.mac.render_kw = {'placeholder': 'aabbccddeeaa'}
 
         r = server.get('/scopes')
         room_id = params['scope-room']