Follow-up to 1612405: Fix mutex usage snafu in named atomics.
Follow-up to 1612405: Fix mutex usage snafu in named atomics.

* subversion/libsvn_subr/named_atomic.c
  (lock): Take out and _keep_ the thread mutex.

Found by: ivan

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1615354 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion