[fix #48160213] downgrade bunny gem to 0.8 version

The 0.9.x version had a bug which used 100% CPU.
0.8.0 is the latest stabile bunny gem.
Merge pull request #164 from ke4/48160213_downgrade_bunny_gem_to_the_latest_stabil_version__0_8_0__

[fix #48160213] downgrade bunny gem to 0.8 version