locktest: remove manual declaration of errno

locktest: remove manual declaration of errno

locktest.c has already #included <errno.h>, so remove the unneeded
(and in some cases, incorrect) manual declaration of errno as an
integer.  Some C libraries use a macro to provide thread-safety for
errno, so it's incorrect to try to provide a manual declaration.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>