Fix for issue #1126: bzr required for some go modules (#1127)

Dockerfile

@@ -1,6 +1,7 @@
 FROM golang:1.12-alpine
 
 RUN apk add --no-cache bash \
+                       bzr \
                        curl \
                        docker \
                        git \

Dockerfile.cgo

@@ -2,6 +2,7 @@ FROM golang:1.12-alpine
 
 RUN apk add --no-cache bash \
                        build-base \
+                       bzr \
                        curl \
                        docker \
                        git \