Remove unused check_docker_server_api_version()

The last code that called it was removed in 1f42a9d2f9

weave

@@ -406,22 +406,6 @@ random_mac() {
 # weave and docker specific helpers
 ######################################################################
 
-check_docker_server_api_version() {
-    # Cope with various versions of `docker version` output format
-    if ! DOCKER_API_VERSION=$(docker version -f '{{.Server.APIVersion}}' 2> /dev/null ) ; then
-        if ! DOCKER_API_VERSION=$(docker version -f '{{.Server.ApiVersion}}' 2> /dev/null ) ; then
-            if ! DOCKER_API_VERSION=$(docker version | sed -n -e 's|^Server API version: *\([0-9][0-9]*\.[0-9][0-9]\).*|\1|p') || [ -z "$DOCKER_API_VERSION" ] ; then
-                echo "ERROR: Unable to determine docker version" >&2
-                exit 1
-            fi
-        fi
-    fi
-
-    if version_lt ${DOCKER_API_VERSION}.0 ${1}.0 ; then
-        return 1
-    fi
-}
-
 util_op() {
     if command_exists weaveutil ; then
         weaveutil "$@"