Extract the debug/namespace flags into run.Config [#67]

This is a general-purpose cleanup commit; every step except InitKube had
the same six "add the --debug and --namespace flags if applicable" code.

internal/run/upgrade.go

@@ -60,15 +60,7 @@ func (u *Upgrade) Prepare() error {
 		return fmt.Errorf("release is required")
 	}
 
-	args := make([]string, 0)
-
-	if u.namespace != "" {
-		args = append(args, "--namespace", u.namespace)
-	}
-	if u.debug {
-		args = append(args, "--debug")
-	}
-
+	args := u.globalFlags()
 	args = append(args, "upgrade", "--install")
 
 	if u.chartVersion != "" {