Fix i18n messages in neutronclient

Using tools/check_i18n.py to scan source directory, and fix most of
the errors.
    - Message internationalization
    - First letter must be capital
    - Using comma instead of percent in LOG.xxx

Partial-Bug: #1217100
Change-Id: I312f999f97e33d84c3f06fa1caacf32affc26a78