Revert "Bump github.com/docker/distribution"

This reverts commit 76abd7b.

go.mod

@@ -20,7 +20,7 @@ require (
 	github.com/blang/semver v3.5.1+incompatible
 	github.com/cloudfoundry/bosh-cli v5.5.1+incompatible
 	github.com/cyphar/filepath-securejoin v0.2.1
-	github.com/docker/distribution v2.8.0+incompatible
+	github.com/docker/distribution v2.6.0-rc.1.0.20171109224904-e5b5e44386f7+incompatible
 	github.com/fatih/color v1.5.1-0.20170926111411-5df930a27be2
 	github.com/google/go-querystring v0.0.0-20170111101155-53e6ce116135
 	github.com/jessevdk/go-flags v1.4.1-0.20181221193153-c0795c8afcf4

go.sum

@@ -127,8 +127,8 @@ github.com/cyphar/filepath-securejoin v0.2.1/go.mod h1:FpkQEhXnPnOthhzymB7CGsFk2
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/docker/distribution v2.8.0+incompatible h1:l9EaZDICImO1ngI+uTifW+ZYvvz7fKISBAKpg+MbWbY=
-github.com/docker/distribution v2.8.0+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
+github.com/docker/distribution v2.6.0-rc.1.0.20171109224904-e5b5e44386f7+incompatible h1:AJ5ylGRVLdpWcAw14qENVOr/M8/s7vApzMorVhyVL78=
+github.com/docker/distribution v2.6.0-rc.1.0.20171109224904-e5b5e44386f7+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
 github.com/docker/docker v1.4.2-0.20171120205147-9de84a78d76e h1:M+/1NNHE/mg+RUox/04+rZoahJVklPfs6xZFECVnxso=
 github.com/docker/docker v1.4.2-0.20171120205147-9de84a78d76e/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
 github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815/go.mod h1:WwZ+bS3ebgob9U8Nd0kOddGdZWjyMGR8Wziv+TBNwSE=