Summary:
People keep breaking the gcc 4.8 compilation due to different
warnings for shadowing member functions with locals. Adding to Travis
to keep compatibility. (gcc 4.8 is default on CentOS 7.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6915
Test Plan: local and Travis
Reviewed By: siying
Differential Revision: D21842894
Pulled By: pdillinger
fbshipit-source-id: bdcd4385127ee5d1cc222d87e53fb3695c32a9d4