LU-14227 tests: Add missing space in sanity-lnet test 21

LU-14227 tests: Add missing space in sanity-lnet test 21

otherwise echo"Add peer with nidrange (gni)" is not a valid command

Change-Id: Ibdff3f38338bb880dd4ae23e31ca2517f4626010
Test-Parameters: trivial testlist=sanity-lnet
Fixes: 6a8335be5c2b ("LU-12410 tests: Add gni tests to sanity-lnet")
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/41003
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>