Remove Google Analytics code

Both the login and dashboard pages include google analytics code. This
is commented out on the dashboard page so has no effect there, but is
live on the login page. This means any time someone tries to log in to
Calamari, their browser will hit Google's server with a bogus Google
Analytics site ID. This seems rather undesirable to me.

Signed-off-by: Tim Serong <tserong@suse.com>
(cherry picked from commit c53946cebaaa7dc64b30de7ef924da3f109eb4b0)
Poll every 500ms to activate login button

There's another variant of issue #8352, where the form is initially
blank, but the user later types in a username which causes Firefox to
autofill the password field at this point in time, rather than on
initial pageload.  This does not trigger an input event, so the submit
button is never enabled.  To workaround this, I've changed setTimeout to
setInterval, so the page continually polls every 500ms.  This also means
we can remove the input event handlers, because the poll will pick up
the changed fields quickly anyway.

Signed-off-by: Tim Serong <tserong@suse.com>
(cherry picked from commit d4cb05ff5d3c9e51150d4f50ffbc2da45d55cab9)