<form role="form" id="registration-form" onsubmit="return onSubmitContinueButton()">

    <div class="row">
        <div class="form-group col-md-6">
            <label class="sr-only" for="xxx"></label>
            <span class="glyphicon glyphicon-name"></span> <!--  <-- there is a breakline after this.... why?-->
            <select class="form-control" name="aaa">
                <option value="1">1</option>
                <option value="2">2</option>
                <option value="3">3</option>
            </select>
        </div>

        <div class="form-group col-md-6">
            <label class="sr-only" for="xxx"></label>
            <span class="glyphicon glyphicon-name"></span> <!--  <-- there is a breakline after this.... why?-->
            <select class="form-control" name="aaa">
                <option value="1">1</option>
                <option value="2">2</option>
                <option value="3">3</option>
            </select>
        </div>
    </div>
</form>

<div class="input-group">
   <span class="input-group-addon" id="basic-addon1"><span class="glyphicon glyphicon-plus"></span></span>
   <select class="form-control" name="aaa">
            <option value="1">1</option>
            <option value="2">2</option>
            <option value="3">3</option>
        </select>
</div>