cvsexportcommit: avoid racy CVS problem.

cvsexportcommit: avoid racy CVS problem.

If git cvsexportcommit is executed fast enough in sequence, the CVS
timestamps could end up being the same. CVS tries to fix this
by sleeping until the CPU clock changes seconds. Unfortunately,
the CPU clock and the file system clock are not necessarily the same, so
the timestamps could be the same anyway. When that happens CVS may not
recognize changed files and cvs will forget to commit some files.

Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>