LP#1886713: fix issue where AngularJS hotkeys fail to initialize

LP#1886713: fix issue where AngularJS hotkeys fail to initialize

Fixes a race condition where the navbar service can look for
eg-accesskey attributes before all of the elements that have
them meet the conditions to show up in the DOM.

To test
-------
[1] From an AngularJS part of the staff interface, note that
    hitting F8 sometimes does not perform the retrieve
    last patron action, nor does F8 show up on the list of
    hot keys when you hit "?" outside of an input.
[2] Apply the patch and repeat step 1. This time, the F8
    hotkey should consistently work.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Rogan Hamby <rogan.hamby@gmail.com>