LU-18162 obdecho: remove LBUG() from echo_device_init()

LU-18162 obdecho: remove LBUG() from echo_device_init()

Remove LBUG() from otherwise unimplemented echo_device_init().

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Idd6c507a546d158438f7b74deb451f70ab15a341
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58802
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>