Update POT file

It is done by the following commands:

  ./tools/generatepot
  msgcat --no-wrap --sort-by-file openstack-ops.pot
Remove obsolete entries in ja.po
Update file location in ja.po
Update ja.po based on the latest POT

msgmerge --previous --update ja.po openstack-ops.pot

The current status is:
2380 translated messages, 179 fuzzy translations, 127 untranslated messages.