Removed duplicated includes

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Closes #11775

cmd/zfs/zfs_main.c

@@ -53,7 +53,6 @@
 #include <grp.h>
 #include <pwd.h>
 #include <signal.h>
-#include <sys/debug.h>
 #include <sys/list.h>
 #include <sys/mkdev.h>
 #include <sys/mntent.h>
@@ -71,7 +70,6 @@
 #include <zfs_prop.h>
 #include <zfs_deleg.h>
 #include <libzutil.h>
-#include <libuutil.h>
 #ifdef HAVE_IDMAP
 #include <aclutils.h>
 #include <directory.h>