GUACAMOLE-630: Do not contain entire field nor entire header within <label>.

Enclosing the entire field within the <label> results in problems when
the field is large and when the field contains multiple interactive
elements. Clicking within interactive elements of a complex field
triggers the <label>, refocusing the first input element. If the field
is large, the <label> will contain empty space which also refocuses the
input field upon being clicked, despite appearing to be the background
of the page.

guacamole/src/main/webapp/app/form/templates/timeZoneField.html

@@ -2,6 +2,7 @@
 
     <!-- Available time zone regions -->
     <select class="time-zone-region"
+            ng-attr-id="{{ fieldId }}"
             ng-model="region"
             ng-options="name for name in regions | orderBy: name"></select>