LU-17431 utils: adapt dynamic use in nodemap_cmd

LU-17431 utils: adapt dynamic use in nodemap_cmd

In nodemap_cmd(), try to detect if we are running on an MGS
before using the dynamic parameter.

Test-Parameters: trivial
Fixes: fecc3bd4e2 ("LU-17431 utils: add 'dynamic' parameter to nodemap_cmd")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I63a727491c839e457e44eaf1f4b4d11b164fd8b4
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55000
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>