Remove GO15VENDOREXPERIMENT

This environment variable is no longer
needed in Go 1.6 (as it's not the default).

Removed this environment variable from
all Dockerfiles except the Dockerfile.s390x,
which is still using gcc 5.3 (Go 1.5)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -179,7 +179,6 @@ RUN set -x \
 # Install notary and notary-server
 ENV NOTARY_VERSION v0.3.0
 RUN set -x \
-	&& export GO15VENDOREXPERIMENT=1 \
 	&& export GOPATH="$(mktemp -d)" \
 	&& git clone https://github.com/docker/notary.git "$GOPATH/src/github.com/docker/notary" \
 	&& (cd "$GOPATH/src/github.com/docker/notary" && git checkout -q "$NOTARY_VERSION") \

Dockerfile.aarch64

@@ -119,7 +119,6 @@ RUN set -x \
 # Install notary and notary-server
 ENV NOTARY_VERSION v0.3.0
 RUN set -x \
-	&& export GO15VENDOREXPERIMENT=1 \
 	&& export GOPATH="$(mktemp -d)" \
 	&& git clone https://github.com/docker/notary.git "$GOPATH/src/github.com/docker/notary" \
 	&& (cd "$GOPATH/src/github.com/docker/notary" && git checkout -q "$NOTARY_VERSION") \

Dockerfile.armhf

@@ -128,7 +128,6 @@ RUN set -x \
 # Install notary and notary-server
 ENV NOTARY_VERSION v0.3.0
 RUN set -x \
-	&& export GO15VENDOREXPERIMENT=1 \
 	&& export GOPATH="$(mktemp -d)" \
 	&& git clone https://github.com/docker/notary.git "$GOPATH/src/github.com/docker/notary" \
 	&& (cd "$GOPATH/src/github.com/docker/notary" && git checkout -q "$NOTARY_VERSION") \