GUACAMOLE-883: Allow guacTextInput directive to lose focus.

guacamole/src/main/webapp/app/textInput/templates/guacKey.html

@@ -1,4 +1,3 @@
-<button class="key" ng-click="updateKey()" ng-class="{pressed: pressed, sticky: sticky}">
-
+<button class="key" ng-mousedown="updateKey($event)" ng-class="{pressed: pressed, sticky: sticky}">
     {{text | translate}}
 </button>