etcd: Rewrite embed etcd implementation

This is a giant cleanup of the etcd code. The earlier version was
written when I was less experienced with golang.

This is still not perfect, and does contain some races, but at least
it's a decent base to start from. The automatic elastic clustering
should be considered an experimental feature. If you need a more
battle-tested cluster, then you should manage etcd manually and point
mgmt at your existing cluster.

util/util_test.go

@@ -22,6 +22,7 @@ package util
 import (
 	"reflect"
 	"sort"
+	"strings"
 	"testing"
 )
 
@@ -1014,6 +1015,76 @@ func TestRemovePathPrefix0(t *testing.T) {
 	}
 }
 
+func TestPriorityStrSliceSort0(t *testing.T) {
+	in := []string{"foo", "bar", "baz"}
+	ex := []string{"bar", "baz", "foo"}
+
+	fn := func(x string) bool {
+		return x == "foo"
+	}
+	out := PriorityStrSliceSort(in, fn)
+
+	if !reflect.DeepEqual(ex, out) {
+		t.Errorf("PriorityStrSliceSort expected: %v; got: %v.", ex, out)
+	}
+}
+
+func TestPriorityStrSliceSort1(t *testing.T) {
+	in := []string{"foo", "bar", "baz"}
+	ex := []string{"bar", "foo", "baz"}
+
+	fn := func(x string) bool {
+		return x != "bar" // != brings this key to the front
+	}
+	out := PriorityStrSliceSort(in, fn)
+
+	if !reflect.DeepEqual(ex, out) {
+		t.Errorf("PriorityStrSliceSort expected: %v; got: %v.", ex, out)
+	}
+}
+
+func TestPriorityStrSliceSort2(t *testing.T) {
+	in := []string{"bar", "foo", "bar", "bar", "baz"}
+	ex := []string{"foo", "baz", "bar", "bar", "bar"}
+
+	fn := func(x string) bool {
+		return x == "bar"
+	}
+	out := PriorityStrSliceSort(in, fn)
+
+	if !reflect.DeepEqual(ex, out) {
+		t.Errorf("PriorityStrSliceSort expected: %v; got: %v.", ex, out)
+	}
+}
+
+func TestPriorityStrSliceSort3(t *testing.T) {
+	in := []string{"foo", "bar1", "bar2", "bar3", "baz"}
+	ex := []string{"bar1", "bar2", "bar3", "foo", "baz"}
+
+	fn := func(x string) bool {
+		return !strings.HasPrefix(x, "bar")
+	}
+	out := PriorityStrSliceSort(in, fn)
+
+	if !reflect.DeepEqual(ex, out) {
+		t.Errorf("PriorityStrSliceSort expected: %v; got: %v.", ex, out)
+	}
+}
+
+func TestPriorityStrSliceSort4(t *testing.T) {
+	in := []string{"foo", "bar1", "bar2", "bar3", "baz"}
+	ex := []string{"foo", "baz", "bar1", "bar2", "bar3"}
+
+	fn := func(x string) bool {
+		return strings.HasPrefix(x, "bar")
+	}
+	out := PriorityStrSliceSort(in, fn)
+
+	if !reflect.DeepEqual(ex, out) {
+		t.Errorf("PriorityStrSliceSort expected: %v; got: %v.", ex, out)
+	}
+}
+
 func TestSortedStrSliceCompare0(t *testing.T) {
 	slice0 := []string{"foo", "bar", "baz"}
 	slice1 := []string{"bar", "foo", "baz"}