Fix DCHECKs in IOBufQueue
Fix DCHECKs in IOBufQueue

Summary: glog actually tries to pull srtings from these pointers when the checks fail, which obfuscates the error

Reviewed By: yfeldblum

Differential Revision: D6506886

fbshipit-source-id: 0283e02aecaa248b84fca1433d3f29f92c37b2e6

facebook/folly,rklabs/folly,facebook/folly,rklabs/folly,facebook/folly,rklabs/folly,rklabs/folly,facebook/folly,rklabs/folly,facebook/folly