Fix duplicated message string in en_US.po file.

The en_US.po file has the same message string to two different message
ID's. The two message ID's are used in different situations and linked
to different messages codes in i18n.pu file. Changed to use the same
content of msgid in msgstr.

Signed-off-by: Paulo Vital <pvital@linux.vnet.ibm.com>