Use golang.org/x/sys/execabs

Signed-off-by: Tibor Vass <tibor@docker.com>

vendor/github.com/docker/cli/cli-plugins/manager/candidate.go

@@ -1,7 +1,7 @@
 package manager
 
 import (
-	"os/exec"
+	exec "golang.org/x/sys/execabs"
 )
 
 // Candidate represents a possible plugin candidate, for mocking purposes

vendor/github.com/docker/cli/cli-plugins/manager/manager.go

@@ -3,7 +3,6 @@ package manager
 import (
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -12,6 +11,7 @@ import (
 	"github.com/docker/cli/cli/config"
 	"github.com/fvbommel/sortorder"
 	"github.com/spf13/cobra"
+	exec "golang.org/x/sys/execabs"
 )
 
 // ReexecEnvvar is the name of an ennvar which is set to the command