[FIX] web: correctly display statusbar

Some status were shown in the statusbar even though they were not specified in
the `statusbar_visible` attribute. This happened when the value was a substring
of one specified value.

Example:
```
hello = fields.Selection([('hello', 'Hello'), ('hello_world', 'Hello World')])
<field name='hello' widget='statusbar' statusbar_visible='hello_world'/>
```
In this case, both status were shown ('hello' is a substring of 'hello_world').

Fixes #20034