Multiple input group addons border issue

Created by: DmitryEfimenko

When you have multiple addons around input the border between them gets doubled.

Example of html markup:

<div class="form-group">
    <label class="control-label" for="UserName">User Name</label>
    <div class="input-group">
        <span class="input-group-addon">1</span>
        <span class="input-group-addon">2</span>
        <span class="input-group-addon">3</span>
        <span class="input-group-addon">4</span>
        <input class="form-control" id="UserName" name="UserName" type="text" value="">
        <span class="input-group-addon">1</span>
        <span class="input-group-addon">2</span>
        <span class="input-group-addon">3</span>
        <span class="input-group-addon">4</span>
    </div>
</div>

Example: jsFiddle