LU-19103 mgs: check mti nid format is old

LU-19103 mgs: check mti nid format is old

Check mti NID list format passed by MGC in addition to
connection flags as real request can be prepared before
flags are negotiated

Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: Ic669be26439bc1ef2f5713c0520af8c1c54fc981
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/59742
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>