[FAB-13752] Cleanup Docker related infrastructure

Removed code made obsolete by recent changes to the
Docker build process

Change-Id: If971ea69ba5a3291afb93d408254be8c861da1cb
Signed-off-by: Brett Logan <Brett.T.Logan@ibm.com>

Author: Brett Logan

docker-env.mk

@@ -49,17 +49,9 @@ BASE_DOCKER_TAG=$(ARCH)-$(BASEIMAGE_RELEASE)
 
 DOCKER_NS ?= hyperledger
 DOCKER_TAG=$(ARCH)-$(PROJECT_VERSION)
-PREV_TAG=$(ARCH)-$(PREV_VERSION)
 
 BASE_DOCKER_LABEL=org.hyperledger.fabric
 
-DOCKER_DYNAMIC_LINK ?= false
-DOCKER_GO_LDFLAGS += $(GO_LDFLAGS)
-
-ifeq ($(DOCKER_DYNAMIC_LINK),false)
-DOCKER_GO_LDFLAGS += -linkmode external -extldflags '-static -lpthread'
-endif
-
 #
 # What is a .dummy file?
 #