fix warnings

`rake run_unitttests` stops because of -Werror
add comment in unused unittest
fix warnings

`rake run_unitttests` stops because of -Werror
add comment in unused unittest
Merge branches 'fix_unittests' and 'fix_unittests' of https://github.com/iHiroakiKawai/trema-edge into fix_unittests
Merge pull request #76 from iHiroakiKawai/fix_unittests

Fix unittests