Update en_US message translations.

Fixes bug 1101587.

* nova/locale/en_US/LC_MESSAGES/nova.po: This "translation" was
woefully outdated, causing KeyError exceptions under a number of
circumstances for users of this particular locale when format
strings wound up containing incorrect substitution variables. This
change attempts to sync up the msgstr entries to match msgid given
this is the source language for the pot file. I did not see any
obvious instances where en_US should differ from C locale for these.

Change-Id: I81d1729fee17653b089f3c47db20f3fc073ab363
Imported Translations from Transifex

Change-Id: Ieacbf1fc844e8c7297658b822baa41bd78dc754d
Merge "Update en_US message translations."
Merge "Imported Translations from Transifex"