Update i18n translation for Mellanox plugin and agent 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 mlnx
directory under neutron/plugins.

Change-Id: Idfdb38360888002b066c8ac2d177a92b2ac173f4
Partial-Bug: #1320867
Merge "Update i18n translation for Mellanox plugin and agent log msg's"