Implements the autocomplete attribute on the login form

The current login form allows the browser to automatically complete the authentication credentials based on saved values. This presents a security risk as described in bug 1116168.

This commit adds the autocomplete attribute to the form tag for the login page to prevent this behaviour.

Change-Id: I1b218b2db787c1581134f9bd80904c161d20b4c3
Fixes: bug #1116168
Merge "Implements the autocomplete attribute on the login form"