remove uses of pkg/stringid.GenerateRandomID()

This utility was only used for testing, and to generate a random
suffix for Dockerfiles. As we don't need the same contract as
pkg/stringid.GenerateRandomID() (not allow all-numeric IDs as they
would not be usable for hostnames), we can use a local test-utility,
and local implementation for the random suffix instead.

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

vendor/github.com/docker/docker/pkg/stringid/stringid.go

@@ -1,63 +0,0 @@
-// Package stringid provides helper functions for dealing with string identifiers
-package stringid
-
-import (
-	"crypto/rand"
-	"encoding/hex"
-	"strings"
-)
-
-const (
-	shortLen = 12
-	fullLen  = 64
-)
-
-// TruncateID returns a shorthand version of a string identifier for convenience.
-// A collision with other shorthands is very unlikely, but possible.
-// In case of a collision a lookup with TruncIndex.Get() will fail, and the caller
-// will need to use a longer prefix, or the full-length Id.
-func TruncateID(id string) string {
-	if i := strings.IndexRune(id, ':'); i >= 0 {
-		id = id[i+1:]
-	}
-	if len(id) > shortLen {
-		id = id[:shortLen]
-	}
-	return id
-}
-
-// GenerateRandomID returns a unique, 64-character ID consisting of a-z, 0-9.
-// It guarantees that the ID, when truncated ([TruncateID]) does not consist
-// of numbers only, so that the truncated ID can be used as hostname for
-// containers.
-func GenerateRandomID() string {
-	b := make([]byte, 32)
-	for {
-		if _, err := rand.Read(b); err != nil {
-			panic(err) // This shouldn't happen
-		}
-		id := hex.EncodeToString(b)
-
-		// make sure that the truncated ID does not consist of only numeric
-		// characters, as it's used as default hostname for containers.
-		//
-		// See:
-		// - https://github.com/moby/moby/issues/3869
-		// - https://bugzilla.redhat.com/show_bug.cgi?id=1059122
-		if allNum(id[:shortLen]) {
-			// all numbers; try again
-			continue
-		}
-		return id
-	}
-}
-
-// allNum checks whether id consists of only numbers (0-9).
-func allNum(id string) bool {
-	for _, c := range []byte(id) {
-		if c > '9' || c < '0' {
-			return false
-		}
-	}
-	return true
-}