Dirty forms check only works for text fields

On JAC currently when you try to assign an issue the assignee can be changed and clicking away from the form will not bring up a dirty form warning. Dirty form warnings only seem to be in place for text fields.

No idea when this regression was introduced but it's also breaking selenium tests on both trunk and branch (https://jira.bamboo.atlassian.com/browse/BRANCH44-FIREFOX36-SEL15-80/test/case/153978638)