Make sslError a string
Make sslError a string

Summary:
Make sslError a string so that we don't have
a dependency on openssl internals.

Reviewed By: knekritz

Differential Revision: D3234146

fb-gh-sync-id: 13eaf5f3a45bb3978cb29e8c1b698a933657431f
fbshipit-source-id: 13eaf5f3a45bb3978cb29e8c1b698a933657431f

facebook/wangle,facebook/wangle,Dalzhim/wangle,facebook/wangle,Dalzhim/wangle