kern/56253: udf_renamerace_cycle test is flaky

[campbell+netbsd%mumble.net@localhost]

>Number:         56253
>Category:       kern
>Synopsis:       udf_renamerace_cycle test is flaky
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 16 23:55:00 +0000 2021
>Originator:     Taylor R Campbell
>Release:        9.99.x
>Organization:
>Environment:
>Description:
Sometimes fails with ENOSPC, like udf_renamerace_dirs:

https://releng.netbsd.org/b5reports/i386/2021/2021.06.16.00.56.16/test.html#fs_vfs_t_renamerace_udf_renamerace_cycle
>How-To-Repeat:
atf-run /usr/tests/fs/vfs/t_renamerace
>Fix:
Yes, please!