MDL-59836 core_amd: Use only one input event handler

MDL-59836 core_amd: Use only one input event handler

* We have duplicate input event handlers for the autocomplete element
which are both firing when the input element's value is being set.
In case an AJAX handler is defined for the autocomplete suggestions,
this causes the autocomplete suggestions so show "No suggestions" first
and then load the results from the AJAX handler a little bit later.