libweave: Remove mime_type from HttpClient interface

This simplifies platform side implementation. The implementation will
just submit all headers as is.

BUG=brillo:1250
TEST=`FEATURES=test emerge-gizmo libweave buffet`

Change-Id: Id7f968fab5c18ca30223e456c04d36c2a0becb7e
2 files changed
tree: 98588ed8107a89126e980e6d6825ad4e7a773695
  1. buffet/