etcdctl: use user specified timeout value for entire command execution

etcdctl should be capable to use a user specified timeout value for
total command execution, not only per request timeout. This commit
adds a new option --total-timeout to the command. The value passed via
this option is used as a timeout value of entire command execution.

Fixes coreos#3517

etcdctl/command/auth_commands.go

@@ -20,7 +20,6 @@ import (
 	"strings"
 
 	"github.com/coreos/etcd/Godeps/_workspace/src/github.com/codegangsta/cli"
-	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
 	"github.com/coreos/etcd/client"
 )
 
@@ -67,7 +66,7 @@ func authEnableDisable(c *cli.Context, enable bool) {
 		os.Exit(1)
 	}
 	s := mustNewAuthAPI(c)
-	ctx, cancel := context.WithTimeout(context.Background(), client.DefaultRequestTimeout)
+	ctx, cancel := contextWithTotalTimeout(c)
 	var err error
 	if enable {
 		err = s.Enable(ctx)