i18n: fix syntax errors in Ukrainian po

"Content-Type: text/plain; charset=UTF-8" was wrote twice in each
of base.po and firewall.po, and one was an incorrect place which
was the cause of the errors.

And, The escape in abbr HTML tag was incorrect, so I fixed it.

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>