Change exit() to _exit() in the child process. exit flushes stdio file buffers,

Change exit() to _exit() in the child process. exit flushes stdio file buffers,
_exit doesn't. If there were some open files, an error in exec and subsequent
exit() would cause the buffers to be flushed twice.

Example:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

int main()
{
	printf("buu");
	if (!fork()) {
		execl("/bin/true-not-exists", "/bin/true", NULL);
		exit(1);
	}
	wait(NULL);
	return 0;
}

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com
---
 daemons/dmeventd/libdevmapper-event.c |    2 +-
 lib/misc/lvm-exec.c                   |    2 +-
 test/harness.c                        |    3 ++-
 tools/dmsetup.c                       |    2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)