mediawiki.page.patrol: Use this.href instead of $(this).attr('href')

mediawiki.page.patrol: Use this.href instead of $(this).attr('href')

This is the difference between prop('href') and attr('href'). The attribute
returns the (usually relative) url authored in the HTML, whereas the property
returns the effective url, which is what mw.util.getParamValue expects.

Also remove the single-use variable and needless use of jQuery
(property access is more idiomatic through, well, properties).

Change-Id: Id8589dbb24869d5a88351daa65d51ab8602f5c77