Utilize multi-stage build to reduce docker image size

This reduces the size of the Docker image from ca. 1.2GB down to about
750MB.

Also, move unit tests from .travis.yml to Dockerfile. Final production
image is not able to run unit tests anymore, as sources are missing from
there.

.travis.yml

@@ -5,4 +5,3 @@ services:
 
 script:
     - docker build -t quay.io/kubernetes_incubator/node-feature-discovery .
-    - docker run --entrypoint=go quay.io/kubernetes_incubator/node-feature-discovery test

Dockerfile

@@ -1,12 +1,10 @@
-FROM golang:1.8 
+# Build node feature discovery
+FROM golang:1.8 as builder
 
-# Build node feature discovery and set it as entrypoint.
 ADD . /go/src/github.com/kubernetes-incubator/node-feature-discovery
 
 WORKDIR /go/src/github.com/kubernetes-incubator/node-feature-discovery
 
-ENV PATH="/go/src/github.com/kubernetes-incubator/node-feature-discovery/rdt-discovery:${PATH}"
-
 ENV CMT_CAT_VERSION="v1.2.0"
 
 ARG NFD_VERSION
@@ -18,7 +16,8 @@ RUN case $(dpkg --print-architecture) in \
         *) \
                 git clone --depth 1 -b $CMT_CAT_VERSION https://github.com/intel/intel-cmt-cat.git && \
                 make -C intel-cmt-cat/lib install && \
-                make -C rdt-discovery \
+                make -C rdt-discovery && \
+                make -C rdt-discovery install \
                 ;; \
         esac
 
@@ -28,4 +27,15 @@ RUN go install \
   -ldflags "-s -w -X main.version=$NFD_VERSION" \
   github.com/kubernetes-incubator/node-feature-discovery
 
-ENTRYPOINT ["/go/bin/node-feature-discovery"]
+RUN go test .
+
+
+# Create production image for running node feature discovery
+FROM golang:1.8
+
+COPY --from=builder /usr/local/bin /usr/local/bin
+COPY --from=builder /usr/local/lib /usr/local/lib
+RUN ldconfig
+COPY --from=builder /go/bin/node-feature-discovery /usr/bin/node-feature-discovery
+
+ENTRYPOINT ["/usr/bin/node-feature-discovery"]