MAGETWO-77672: <![CDATA[]]>in system.xml translate phrase not work, if comment starts from new line.

[nmalevanec]

Description

Fix for <![CDATA[]]> in system.xml translate phrase not work, if comment has spaces after opening tag, or before closing one(for instance: comment starts on new line). Ex:

<comment>
<![CDATA[Some comment]]>
</comment>

Fixed Issues (if relevant)

1. <![CDATA[]]>in system.xml translate phrase not work  #7767: in system.xml translate phrase not work

Manual testing scenarios

1. Create a module which has system.xml
2. In the system.xml:

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <tab id="foo_bar" translate="label" sortOrder="200">
            <label>Foo/Bar</label>
        </tab>
        <section id="foo_bar" translate="label" type="text" sortOrder="40" showInDefault="1" showInWebsite="1" showInStore="1">
            <class>separator-top</class>
            <label>Foo/Bar</label>
            <tab>foo_bar</tab>
            <resource>Magento_Catalog::config_catalog</resource>
            <group id="test" translate="label" type="text" sortOrder="90" showInDefault="1" showInWebsite="1" showInStore="1">
                <field id="test" translate="label comment" type="text" sortOrder="20" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Test phrases</label>
                    <comment>
                        <![CDATA[Some test comment here.]]>
                    </comment>
                </field>
            </group>
        </section>
    </system>
</config>

3. Use the command to collect the phrases:
   bin/magento i18n:collect-phrases -o "/path_to_your_module/i18n/en_US.csv" path_to_your_module/dir
4. Make some changes to translation in generated en_US.csv ex:
   "Some test comment here. add something new here "
5. Clean cache.
6. Navigate to admin>stores>configuration>Foo/Bar/>Foo/Bar/
7. Check comment for field "Test phrases". It should has add something new here modification You have made in en_US.csv.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)