bootstrap: fallback to default known_hosts

Use default known_hosts and ssh configuration when no private key file
is provided while bootstraping using ssh.

Signed-off-by: Sanskar Jaiswal <jaiswalsanskar078@gmail.com>

cmd/flux/bootstrap_bitbucket_server.go

@@ -174,14 +174,15 @@ func bootstrapBServerCmdRun(cmd *cobra.Command, args []string) error {
 	}
 	defer os.RemoveAll(tmpDir)
 
+	clientOpts := []gogit.ClientOption{gogit.WithDiskStorage(), gogit.WithFallbackToDefaultKnownHosts()}
 	gitClient, err := gogit.NewClient(tmpDir, &git.AuthOptions{
 		Transport: git.HTTPS,
 		Username:  user,
 		Password:  bitbucketToken,
 		CAFile:    caBundle,
-	})
+	}, clientOpts...)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to create a Git client: %w", err)
 	}
 
 	// Install manifest config