Build and install from GOPATH

* Rename 'vendor/src' -> 'vendor'
  * Ignore vendor/ instead of vendor/src/ for lint
* Rename 'cmd/client' -> 'cmd/ocic' to make it 'go install'able
* Rename 'cmd/server' -> 'cmd/ocid' to make it 'go install'able
* Update Makefile to build and install from GOPATH
* Update tests to locate ocid/ocic in GOPATH/bin
* Search for binaries in GOPATH/bin instead of PATH
* Install tools using `go get -u`, so they are updated on each run

Signed-off-by: Jonathan Yu <jawnsy@redhat.com>

vendor/github.com/containers/storage/pkg/stringid/stringid.go

@@ -0,0 +1,71 @@
+// Package stringid provides helper functions for dealing with string identifiers
+package stringid
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/containers/storage/pkg/random"
+)
+
+const shortLen = 12
+
+var validShortID = regexp.MustCompile("^[a-z0-9]{12}$")
+
+// IsShortID determines if an arbitrary string *looks like* a short ID.
+func IsShortID(id string) bool {
+	return validShortID.MatchString(id)
+}
+
+// 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:]
+	}
+	trimTo := shortLen
+	if len(id) < shortLen {
+		trimTo = len(id)
+	}
+	return id[:trimTo]
+}
+
+func generateID(crypto bool) string {
+	b := make([]byte, 32)
+	r := random.Reader
+	if crypto {
+		r = rand.Reader
+	}
+	for {
+		if _, err := io.ReadFull(r, b); err != nil {
+			panic(err) // This shouldn't happen
+		}
+		id := hex.EncodeToString(b)
+		// if we try to parse the truncated for as an int and we don't have
+		// an error then the value is all numeric and causes issues when
+		// used as a hostname. ref #3869
+		if _, err := strconv.ParseInt(TruncateID(id), 10, 64); err == nil {
+			continue
+		}
+		return id
+	}
+}
+
+// GenerateRandomID returns a unique id.
+func GenerateRandomID() string {
+	return generateID(true)
+
+}
+
+// GenerateNonCryptoID generates unique id without using cryptographically
+// secure sources of random.
+// It helps you to save entropy.
+func GenerateNonCryptoID() string {
+	return generateID(false)
+}