travis: temporarily disable rustfmt ci check until #4742 is resolved
travis: temporarily disable rustfmt ci check until #4742 is resolved

graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust