Regenerate POT (English PO) files

If POT files contains translated messages, Transifex seems to use
msgstr rather than msgid as index, and this leads to incorrect
source language strings in Transifex [1].
POT files should not have any strings in msgstr to avoid this problem.

This commit regenerates POT files from scratch.

[1] http://lists.openstack.org/pipermail/openstack-i18n/2013-September/000103.html

Closes-Bug: #1226428
Change-Id: I9aa11323edbfd98b95bbc2c26be337cc77df5e87
Merge "Regenerate POT (English PO) files"