Fix coverity defects

1.coverity scan CID:147445 function zfs_do_send in zfs_main.c
Buffer not null terminated (BUFFER_SIZE_WARNING)

2.coverity scan CID:147443 function zfs_do_bookmark in zfs_main.c
Buffer not null terminated (BUFFER_SIZE_WARNING)

3.coverity scan CID:147660 function main in zinject.c
Passing string argv[0] of unknown size to strcpy
By the way, the leak of g_zfs is fixed.

4.coverity scan CID: 147442 function make_disks in zpool_vdev.c
Buffer not null terminated (BUFFER_SIZE_WARNING)

5.coverity scan CID: 147661 function main in dir_rd_update.c
passing string cp1 of unknown size to strcpy

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: luozhengzheng <luo.zhengzheng@zte.com.cn>
Closes #5130

tests/zfs-tests/cmd/dir_rd_update/dir_rd_update.c

@@ -63,6 +63,11 @@ main(int argc, char **argv)
 	}
 
 	cp1 = argv[1];
+	if (strlen(cp1) >= (sizeof (dirpath) - strlen("TMP_DIR"))) {
+		(void) printf("The string length of mount point is "
+			"too large\n");
+		exit(-1);
+	}
 	(void) strcpy(&dirpath[0], (const char *)cp1);
 	(void) strcat(&dirpath[strlen(dirpath)], "TMP_DIR");