Mention macro is incorrectly generating whitespaces in the HTML

A wiki syntax like this

test {{mention reference="XWiki.kbernick" anchor="XWiki-kbernick-i3phd9"/}} text after

in a wiki page in XWiki/2.1 syntax seems to generate the following html:

<p>test <a class="xwiki-mention user" data-reference="xwiki:XWiki.kbernick" href="/xwiki/bin/view/XWiki/kbernick" id="XWiki-kbernick-i3phd9">
@Karsten Bernick
</a> text after</p>

(the newlines in the html above are the original ones).

The newlines between the a tag and the label of the anchor element are actually relevant in HTML, they become whitespaces and are normalized together with the following whitespaces (the regular whitespace between the a ad the text) causing issues like XWIKI-20500 .

Expected markup:
There is no reason for the mention macro to not generate fully inline HTML, like this

<p>test <a class="xwiki-mention user" data-reference="xwiki:XWiki.kbernick" href="/xwiki/bin/view/XWiki/kbernick" id="XWiki-kbernick-i3phd9">@Karsten Bernick</a> text after</p>

with no newlines or spaces at all inside the a tag or in its label.