Update i18n translation for ML2 plugin log msg's

All the existing LOG.info, LOG.warning, LOG.error and LOG.critical
messages should have _LI, _LW, _LE and _LC respectively.
 Also, debug level log shouldn't be translated.

This patch set will cover the ml2 directory under neutron/plugins.

Partial-Bug: #1320867
Change-Id: I9d78d23bbc14e7c536c6ddf2dc4f52c67faeb667