rust-chg: exclude futures-dependent modules from build and break things
It's impractical to upgrade the codebase incrementally since futures 0.1
and 0.3 APIs are fundamentally different. So this patch temporarily excludes
futures-dependent modules from the build. These modules will be upgraded
and re-enabled one by one.
Differential Revision: https://phab.mercurial-scm.org/D8440