[Tails-l10n] Translated variables in zh_CN.po

Hi,

While preparing tails 4.0~beta1 I noticed that the Chinese translations just got messed up by the translator translating variable names:

    ERROR: tmp/tor-translation/zh_CN.po:
            i18nspector is not happy:
                    E: python-brace-format-string-unknown-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": '卷名称' in msgstr but not in msgid
                    E: python-brace-format-string-unknown-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": '错误信息' in msgstr but not in msgid
                    E: python-brace-format-string-missing-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": error_message not in msgstr while in msgid
                    E: python-brace-format-string-missing-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": volume_name not in msgstr while in msgid
    ERROR: po/zh_CN.po:
            i18nspector is not happy:
                    E: python-brace-format-string-unknown-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": '卷名称' in msgstr but not in msgid
                    E: python-brace-format-string-unknown-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": '错误信息' in msgstr but not in msgid
                    E: python-brace-format-string-missing-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": error_message not in msgstr while in msgid
                    E: python-brace-format-string-missing-argument msgid "Couldn't lock volume {volume_name}:\n{error_message}": volume_name not in msgstr while in msgid
checked files are not clean.

Run this with any Tails branch checked out to reproduce:

    ./import-translations  && \
    ./refresh-translations && \
    ./submodules/jenkins-tools/slaves/check_po

Cheers!