Added poll_frequency to wait_until_element and wait_for_ajax

When waiting for spinner or progress bar it's desired to have
increased poll_frequency rather than a default of 0.5 secs.

This may avoid high CPU usage seen while spinner or progress bar.

Also fixed few content view test-cases.
Can this be pushed higher up in the list of conditionals? The resultant logic would look like this:

    if submenu_element is None:
        raise ...
    if tertiary_menu_locator:
        ...
    else:
        ...