LU-18751 lnet: fix sanity-lnet/410 test case

LU-18751 lnet: fix sanity-lnet/410 test case

The use of '\0' is not supported in all versions of bash.
Using "" as a NUL input serves the same purpose.

Test-Parameters: trivial
Fixes: 30868de940 ("LU-18751 lnet: Segfault in lnetctl fault command")
Signed-off-by: Frank Sehr <fsehr@whamcloud.com>
Change-Id: I2caafee1b3e00f1921a7bb2675187353797a0570
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58376
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>