mount: enable debug logging for the flaky TestMount test

The test case fails from time to time with an Input/Output error while
trying to access the snapshots directory.

cmd/restic/integration_fuse_test.go

@@ -12,6 +12,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
 	rtest "github.com/restic/restic/internal/test"
@@ -159,6 +160,11 @@ func TestMount(t *testing.T) {
 		t.Skip("Skipping fuse tests")
 	}
 
+	debugEnabled := debug.TestLogToStderr(t)
+	if debugEnabled {
+		defer debug.TestDisableLog(t)
+	}
+
 	env, cleanup := withTestEnvironment(t)
 	// must list snapshots more than once
 	env.gopts.backendTestHook = nil